I don't see the same error.
Frankly I don't even know if the error was because of firefox installation.
While I was installing 3.5 I was surfing the web and a window popped up.
So I just closed it even without reading the head.
So far i have tried are followings;
Uninstalled 3.xx x86_64 version of firefox and installed 2.0.xx x86_64. Version 2.0.xx works fine. No problem. So I updated to 3.0.11 but doesn't work. No error during update but even 3.0.11 does not work anymore. Updated to 3.5 again while 3.0.11 is installed. Does not work.
It seems completely broken now.