I just ran into an interesting situation on my daughter's MacBook (Mac OS X 10.5.8). Safari (5.0.6) in her user account will not play Flash clips ('missing plugin'), even though the requisite plugins are installed for everyone (Library/Internet Plug-Ins), and Flash works fine in the only other account. Curiously, in the problem account Safari won't stop trying to display the Installed Plug-ins (Help menu) screen either, but the relevant resource file (Plug-ins.html) loads fine in the other account and elsewhere. The only other clue I've got so far is that when I open certain other web pages while Safari is churning away on that Plug-ins.html file, I get slow script errors for that file.

This clearly looks like an account based issue, and running the Mac OS X 10.5.8 Combo installer or the Safari 5.0.6 installer won't help. I wonder if anybody has a clue as to what's florfed, and whether it can be fixed without setting up another account and moving her Home folder there.

Sorry for hitting on the obvious, but is Safari > Prefs > Security (or whatever it is in v 5.0.6) > Web content > Enable plug-ins checked?

Yes, the necessary check boxes are properly set. (But checking—again—never hurts.)

In that case, it may pay to trash the plist. (Sounds like you haven't yet.)

Trashing the com.apple.Safari.plist doesn't help. I'm now checking various items present in ~/Library/Safari. I'm also looking into a possible JavaScript issue, but this may be an unrelated phenomenon.

Might a Safari extension, such as Ghostery, Click to Flash, or Click to PlugIn be installed and thus precluding the plugin from running? If so, you might try disabling the extension(s) and restarting to see if that puts things to right.

Good suggestion, and one I already tested without improvement: extensions ON or OFF doesn't change anything. ClickToPlugin still shows that no plugins are enabled, despite their presence in /Library/Internet Plug-Ins.
If HTML5 clips are available on video sites like YouTube they play fine, if it's only Flash the source claims the clip is not available. Meanwhile, Flash does work in Firefox (11.0) in the affected account. It's Safari that's acting up.

Considered uninstalling/reinstalling ClickToPlugin?

Yes, and I have done so to no effect. (I fixed ClickToPlugin's name in my previous post, thanks). It still says that I don't have any plugins enabled, which is indeed what things look like, despite the presence of plugins in the Libraries.

It remains odd (and significant, I'm sure) that Safari is unable to load the Installed Plug-Ins page from the Help menu. And, interestingly, Adobe's Flash download page will also cause a slow script error. As with the slow script error with Safari's attempt to read/display /Applications/Safari 5.0.6.app/Contents/Resources/English.lproj/Plug-ins.html, tinkering with its tab like attempting to close it will crash Safari. Something sure is messed up here. Time to scrutinize some more Console logs.

Tried SafeBoot yet?

Yes. Safe Boot doesn't change the availability of Safari plugins (as measured a.o. by ClickToPlugin) or the inability of Safari to load the Installed Plug-Ins page. Not that it matters, but I haven't yet looked much beyond that.

In the process of trying things like reinstalling the FlashPlayer plugin and testing its effect I experienced a number of crashes. Looking over the relevant crash logs I get (several cases of) the following crash types. In almost all* cases the affected process was Safari, and I list the salient details:

Process: Safari
Path: /Applications/Safari 5.0.6.app/Contents/MacOS/Safari

(Example 1)
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS
Thread 0 Crashed:
0 com.apple.JavaScriptCore

(Example 2)
Exception Type: EXC_BAD_ACCESS (SIGBUS)
Exception Codes: KERN_PROTECTION_FAILURE
Thread 0 Crashed:
0 com.apple.WebCore

(Example 3)
Exception Type: EXC_BAD_ACCESS (SIGBUS)
Exception Codes: KERN_PROTECTION_FAILURE
Crashed Thread: 19
Thread 19 Crashed:
0 com.apple.QuartzCore

At this moment I haven't yet reproduced exactly what (if anything) I was doing to precipitate a particular crash, like trying to close a particular Safari tab etc.


*) The remaining two cases involved the Adobe Flash Player Installer Manager with an EXC_BREAKPOINT (SIGTRAP) as Exception Type, but virtually no useful data beyond that. Obviously, at these occasions I was trying to see if reinstalling the Flash plugin would make a difference. It did not. And these AFPIM crashes were only noticeable in Console's CrashReporter log; at desktop level there were no indications that anything went wrong, as opposed to the Safari crashes.

I seem to recall that having ClickToFlash and ClickToPlugin installed simultaneously was not advised by the developer. I was unable to find a reference to that piece of information, but if you have both installed, try uninstalling one of them.

Thanks for the suggestion, Jon. I believe it is a special case of the suggestion made by Pendragon earlier in this thread. In any case, there is no difference whether either one, both or neither ClickToXXX plugin(s) are installed or enabled.

Btw, closing the Safari window that's trying to load the Installed Plug-Ins page reliably causes the crash described in Example 1 above.

I wonder whether a deep cache cleaning with applejack AUTO or the like would be worth the effort?

Can't hurt, and might tell us something we don't already know: running <applejack auto restart> as we speak.

Well, not surprisingly, that too didn't make a difference, as it affects only System stuff. I'll run it again in interactive mode, to have a look at the problem account's user caches. That will likely be an overwhelmingly long list, but I might get inspiration from recognizing potential 'goodies' there.

Update
Well, so much for that inspiration: all user caches were emptied without further input (forgot about that, duh! ), but at least I can check them in Applejack's log should this clearing help. FWIW, only two malformed (and quite irrelevant) prefs files were found. Of course, that still allows for multitudes of properly syntaxed but nonetheless corrupted prefs. That said, cleaning all user's caches didn't help: loading the Installed Plug-Ins page afterward once again caused an Example 1 Safari crash.

> running <applejack auto restart> as we speak

I don't know whether it would have made a difference...probably not, but "applejack AUTO," as I suggested, does a deeper cache clear than "auto."

Thanks, I'm aware of that. If you read the rest of that ReadMe, you'll see the recommendation to run the 'AUTO' command after 'auto' in case the latter doesn't help. In my case neither mode helped, likely because both affect System files, and the issue appears to be account-specific. That's why I also ran the interactive mode to clear user caches, which didn't help either.

It looks like a new User account and Home folder data migration is in order. Any suggestions, tips or hints that might expedite things or prevent permission issues etc. down the line?

But if it's a user-specific issue, migrating your daughter's home folder may/will likely perpetuate it; it may pay to try moving all of ~/Library/Prefs to her desktop first.

I only intend to move data files, iTunes library contents, email etc. As it happens, I have moved that Preferences folder temporarily to the Trash as part of my troubleshooting. It had no effect on the phenomena I described above.

This kind of head-scratcher hasn't come up in a while; it would be a shame to have to throw in the towel, but... Oh, well.

(Did you ask your daughter whether she's maybe done something lately that may have brought this on...d/l'ed something, I dunno...?)

So far this effort has not produced information to fix the problem, and now seems to have passed the point of diminishing returns. Because of the available workarounds there is no particular rush, but sooner or later the issue needs to be addressed.

As to downloading 'something': her Downloads folder is filled with files from years, but she doesn't recall anything 'different' happening afterward. Likewise, she rarely empties her Trash, and uses the Desktop to store boatloads of pictures, music files etc. That I take care of whenever I run updates for her every few months or so. The Downloads folder is something else, though, and sorely in need of organizing, stowing away, trashing and backing up. Clearly, she's not amenable to sensible 'management suggestions'...

Anyway, because of possible malware I plan to run MacScan overnight, and see what' it comes up with, if anything. That is, if I can get ahold of her MB: she just absconded with it...

My final thought before throwing in the towel... Has your daughter got anything in ~/Library/Internet Plug-Ins that may be causing a conflict?

No. There was nothing there when I started looking into the problem. I installed some plugins there as part of my troubleshooting, but nothing that hadn't been in /Library/Internet Plug-Ins before, and it didn't make a difference.

PS, MacScan didn't find anything beyond some tracking cookies. Removal, once again, didn't make any difference.

Oh, well...

I have just experienced the same problem, but it also extended to Mail. Mail attachments were represented by the same "missing plugin" as your daughter saw in Safari, and it was seen in Safari as well. I did everything you and everyone else in this forum has suggested and got the same results you got: Zip.

While reading the posts on this topic, I saw Java mentioned a lot. I realized that I had recently turned Java off(last week) on Apple's advice due to security fears. This is on a dual G5 running 10.5.8, and Safari 5.0.6. Turning Java back on solved the problem. If your daughter has a G5 machine this should do it, without making her vulnerable because the OS for Intel machines is different.

I don't believe that this is true. Java is cross-platform and it shouldn't make any difference whether you are using PPC or Intel, or even Windows.

Someone correct me if I'm wrong.

Thanks for your suggestion, and for revisiting this thread. My daughter's MacBook is an Intel based Mac, so it's different from your PPC Mac. That said, I'm still running a 2005 G5 iMac, with 10.5.8 and Safari 5.0.6, AND Java turned off in the latter. No problems like 'missing plugin' here (nor in Mail), and no problems with Flash clips either. So turning Safari's Java plugin on or off doesn't cause the problem in and by itself. What you're seeing may be some kind of interaction, albeit an interesting one.

As it is, the problem MacBook isn't at hand, so I cannot check right away if turning Java back on will help, but given what I mentioned above I'd be surprised if it would. Still, it's easy enough to give it a shot. And while we're on the topic, I'd like to make sure exactly how you turned off Java on your Mac. Was that via the Java plugin in Safari's preferences Security pane, via the actual Java installation, or both?

Btw,
This is a misconception. While PPC Macs cannot run Java 7, the older versions they can run remain vulnerable to a slew of exploits. All you need is visit an appropriately subverted site with Safari and its Java plugin enabled to get hit by e.g., Java 5-based malware.

It wasn't the Safari Java plugin that I turned off, got the problem, turned on and the problem disappeared. It was Java Preferences (Applications-Utilities-Java Preferences). There were two versions of Java there, and I turned on J2SE 5.0. This fixed the "missing plugin" problem with certain mail attachments and also in Safari, where hit counters on several sites gave me the same thing. Apparently, in Leopard, Java is used in Mail to view non-image attachments like text files, and at least some of these Safari hit counters use Java. About vulnerability, I guess I have to choose between being able to see and work with attachments and a possible exploit.

A workaround is to use the QuickLook and Save options in Mail. The attachment files themselves live in the Mail Downloads folder in the User folder. I think I'll take my chances of an exploit to be able to work with attachments hassle-free.

Thanks for the clarification. Turning off Java with its preference utility makes sense against the backdrop of your symptoms. For completeness sake I have to add that I have Java 5 enabled in Java Preferences, but keep Safari's Java plugin turned off to block drive-by problems during surfing. This allows me to run local Java based apps without exposing myself to external threats.

For completeness sake, I'll check if my daughter's Java is enabled in Java Preferences, but I wonder if you had problems playing Flash clips with Java turned off ('my' initial symptom). If not, we're likely talking about two different reasons our 'missing plugin' messages appeared.