I have never had this problem before.
System extension cannot be used
The system extension “//System/Library/Extensions/AppleUSBEthernetHost.kext” was installed improperly and cannot be used. Please try reinstalling it, or contact the products vendor for an update.
This was the message that appeared after I installed the new iTunes Update for 11.4 today.
I have an iMac 2.7 GHz Intel Core i5 with 8 GB memory, I have System 10.9.4
I reinstalled iTunes after removing the AppleUSBEthernetHost.kext and same message. I went back and looked at the previous version in Time Machine of the file and it was the same 7.0. Everything seems to be working okay. Any suggestions are appreciated. The forums had 3 other people write in with no solutions.

I too have the same message popping up on our iMac. I checked the system updates and it updated to 11.4 automatically this morning. Not sure whether I need to do something, everything seems to be working as normal as far as I can tell. Presumably they'll release a fix if it's to do with the update?

Same error here using OSX and 3.2 GHZ i3.

As an experiment, I redownloaded iTunes from Apple Site and TURNED OFF my iPad. Turned it off not put it to sleep and reinstalled and all went well. I do not have an iPhone and the iPad is my only extra apple device. There was no message this time and so far so good. Mark

Same error message using with 2.5 GHz and 4GB memory.

Same thing happening to me. Stupid, stupid Apple and their updates.

Hardware Overview:

Model Name: MacBook Pro
Model Identifier: MacBookPro8,2
Processor Name: Intel Core i7
Processor Speed: 2 GHz
Number of Processors: 1
Total Number of Cores: 4
L2 Cache (per Core): 256 KB
L3 Cache: 6 MB
Memory: 8 GB
Boot ROM Version: MBP81.0047.B27
SMC Version (system): 1.69f4
Sudden Motion Sensor:
State: Enabled

Such bugs (due to apparent lack of attention to detail*) seem to occur every time Apple posts an update.
If this one is as widespread as it appears to be, iTunes 11.4.1 should be showing up on their Support-Download site in short order.

* In the old days parsimony, elegance and debugging were the hallmarks of application design, given the pragmatic necessity occasioned by extraordinarily small memory capacity of computers. Nowadays sloppiness in design and lack of efficient debugging seem to be the acceptable rule.

I tried to install a software update on my macbook this morning and am now getting the same message. Help?

Are you saying there might have been an interaction between your iTunes installation and your iPad?

I installed iTunes this morning and did not see that error message. Maybe Apple surreptitiously fixed it in the later install? Your successful reinstallation may reflect this.

Would be useful for all of you to post which version of OS X you're running.

Did all of you who are getting this error install the iTunes 11.4 update beforehand?

I'm having the same problem:
OSX 10.9.4
2.8 GHz INtel Core i5 Imac 8GB memory

Same problem here. The error message just popped up. I cannot think of anything I might have done to cause the problem, and am wondering what the consequences of doing nothing will be.

MacMini running 10.9.4

By the way, has anyone found a solution to the iconservicesagent problem? (I am aware of the workaround (mkdir ...), but am wondering if there is a solution.)

Had the same problem here today with this popping up after installing the update to iTunes 11.4.

System extension cannot be used
The system extension “//System/Library/Extensions/AppleUSBEthernetHost.kext” was installed improperly and cannot be used. Please try reinstalling it, or contact the product’s vendor for an update.

OSX 10.8.5
3.06 GHz Intel Core 13
4 GB 1333 MHz RAM

I don't 'tether' anything to my desktop but would still like to know what, if anything, I need to do. Will iTunes still be able to install future updates?

Ik ook in nederland ( The Netherlands) me too does Apple het the solution for us

Oke komt het:

MacBook Pro
Software OS X 10.9.4 (13E28):
Serienummer W8046DQTAGU:
Videokaart Intel HD Graphics 288 MB:
Geheugen 4 GB 1067 MHz DDR3:
Processor 2,4 GHz Intel Core i5:
15-inch, medio 2010:
Modelaanduiding: MacBookPro6,2
Processornaam: Intel Core i5
Processorsnelheid: 2,4 GHz
Aantal processors: 1
Totale aantal cores: 2
L2-cache (per core): 256 KB
L3-cache: 3 MB
Geheugen: 4 GB
Interconnectsnelheid processor: 4.8 GT/s
Opstart-ROM-versie: MBP61.0057.B0F
SMC-versie (systeem): 1.58f17
Serienummer (systeem): W8046DQTAGU
Hardware-UUID: B52B7B19-B371-5526-B3FD-A0B45EB2C54E
Sudden Motion Sensor:
Status: Ingeschakeld

Reply to: cyn

Posted moments earlier but replying to this post again here ...

I have ... Version 10.8.5

... and yes, I installed the iTunes 11.4 update just BEFORE the message popped up. I have checked and so far iTunes is working fine on my computer. Just wondering what, if anything, I need to do and if there will be problems with future updates to iTunes. Thanks so much!

Same problem immediately after installing iTunes update.

OS X 10.7.5

I also had this message after installing iTunes 11.4. I ran my OS 10.6.8 Combo installer and have not experienced any problems since.

Same problem just now when installing the iTunes 11.4 update.

Running 10.7.5 on a 2.4GHz i5 MacBook Pro.

Anyone have any idea what the error means? Otherwise this thread will continue to just be one "me too" after another.

This is the best post I can find: https://discussions.apple.com/thread/6526427

I used Pacifist to remove the .kext file from the iTunes install package and replaced the old .kext in the System/Library/Extensions folder. Seems to be working okay on 10.6.8 and 10.9.4.

Hello All-

I had the AppleUSBEthernetHost.kext problem when downloading iTunes 11.4. This is a widespread problem, many forums have addressed it.

I found help here: https://www.discussions.apple.com/message/26574841#26574841

See Lanny’s post, I did as he suggested.
1st- Close iTunes.
2nd- Delete the system extension “AppleUSBethernetHost.kext” from here:
//System/Library/Extensions/AppleUSBethernetHost.kext

3rd- go to iTunes 11.4 download, here: https://www.apple.com/itunes/download/
click on the Download Now link.

4th- Find the downloaded iTunes11.4.dmg file, open it, now open the Install iTunes.pkg

After the re-install as above I got the successfully installed window and no “pop up”
improperly installed AppleUSBMultitouch.kext warning window.

Robes

My System:
27" iMac 2.8 GHz Quad Core i7; 8 GB DDR3 SDRAM 2x4; 2 TB Serial ATA Drive; ATI Radeon HD 4850 Graphics with 512 MB; Using 10.9.4 Mavericks. AudioEngine A5's

Totally agree. Against my better judgment I hit Update on itunes, even though I have no ios8 device. So I had to do the manual remove kext, download, reinstall iTunes. This is the reason I stopped updating my Airport express and any other Apple app that says "improvements" for connection to Cloud, ios, or anything else I do not use. It is not worth the headache to have to fix something that wasn't broken to start out with.

Thanks Robes, that seems to have done the trick for me. I just want to point out to everyone I too had my iPad connected when I first installed the system update from Apple. This time when I reinstalled iTunes I disconnected the ipad first.

I did post it and where is the answhere?

This response earlier in this thread should help you with the solution.....

I'm certain that it's the "english as a 2nd language", however, I don't see where you identified your operating system version of OS X in your previous posts....I do see that you are on a mid-2010 15" MacBook Pro with 4 GB of ram.

Let us know if the quoted post above is helpful and thank you for joining us here.

Cee did provide that info...

Post #31149:

Oke komt het:

MacBook Pro
Software OS X 10.9.4 (13E28):

Actually, welcomes to FTM are in order not just for Cee, but for all 14 new members who participated in this thread.

Echoing MacManiac, thanks for joining us here.

Edit: And going one step further, please stick around; there's much to be learned.

[HeadSlap]"Doah!!!"[/HeadSlap]....

In my case it's english as a 1st language where I experience problems in seeing the entire message....

I also had this pop up. (Followed instructions on reinstall from further down/up this thread.)

One thought I had was - could this have been caused, perhaps in some small part, by the forced download of U2's new album? Could the program (iTunes) be actively looking for mobile devices to dl to? And when it can't locate any or can't properly connect, it fires off this error message. Perhaps that's why turning off an iPad then reinstalling iTunes seemed fix the problem.

Just a thought. At any rate, thanks Robes for the fix!

This might help affected users:
Apple’s new website allows iTunes users to delete U2 album they never asked for

Here's Apple's support documentation – pay attention to the "fine print":
Remove iTunes gift album "Songs of Innocence" from your iTunes music library and purchases (http://support.apple.com/kb/HT6439)

Just wanted to say thanks for posting this fix. I applied it this morning and so far, things seem to be OK.