Apparently there are now testing builds of Firefox that fix some of the bugs I mentioned previously. These will be in one of the 3.5 releases when they come around. There is much discussion about what is actually fixed, but for now I am forced to click through many authentication dialogs when I restart Firefox.
The other bug where Firefox would not save the proxy authentication details for one user is implicitly linked to the “remember passwords for sites” option. Personally I think they should be separate, but as both use HTTP basic authentication there is probably a very good reason for it.
In the spirit of finding more bugs, Rhythmbox also suffers when proxy authentication is enabled. The error
"glib.GError: Proxy Authentication Required" hides on stderr (visible only if you run from the console) when attempting to play last.fm stations. Podcasts generate the cryptic “Error in podcast” (presumably because Squid returns a
text/html page with the error details). Fortunately for radio stations the error is much clearer. The cause of all this pain is a bug in gvfs, noted and fixed in Gnome bugzilla as bug 586922. Ubuntu Karmic (9.10) is currently in testing and includes these fixes, so I will shortly update and see.