Specifically, the problems manifest only in Safari, which either won’t display certain Google and Google-related pages properly, and is completely incapable of loading others. That includes Youtube (text-only), Google Maps (no image) and certain blogs (no go, period). And no, Little Snitch or browser extensions are not to blame. In addition, Safari complains of issues with Google certificates, which AFAICT are identical to the set in the other accounts without the problem. I tested to see if removing all items from the Safari and Keychain folders in ~Library improved matters. It did not. Likewise, Console logs weren’t particularly illuminating either (e.g., no crashes). What am I missing?
Have you tried resetting Safari? In Safari version 8 (which is what I assume you're running now in Yosemite), I see
Safari→Clear History and Website Data and
Safari→Preferences→Privacy→Remove All Website Data. (I assume the former includes the latter.) If you have the Develop menu enabled, there is also
Develop→Empty Caches. (You enable the Develop menu with
Safari→Preferences→Advanced→Show Develop menu in menu bar.)
Safari caches stuff in
~/Library/Caches/com.apple.Safari,
"$TMPDIR"/../C/com.apple.Safari", and in
"$TMPDIR"/../C/WebKitPlugin-*. That should all get cleaned out if you Empty Caches, but it might be worth a look-see.
