This is completely bonkers. I have never seen such silliness before. Any ideas what is going on?

Not the slightest idea, so please excuse my rambling... I googled around a bit for "_disableObsoleteExtensions" and it looks like you are not alone, although I didn't find any magic answers. By strange coincidence, KDE seems to be mentioned frequently. Maybe you could test under a different WM? Another wild guess (grasping at straws now) is that maybe firefox is trying to use libraries from thunderbird or mozilla? Check this as root vs normal to see if there is any difference: % echo $LD_LIBRARY_PATH % echo $MOZILLA_FIVE_HOME % type -ap firefox % ldd /path/to/firefox/firefox-bin If all else fails, you might try posting to http://forums.mozillazine.org/ - Jeff . __________________________________ Do you Yahoo!? Yahoo! Mail - now with 250MB free storage. Learn more. http://info.mail.yahoo.com/mail_250