Someone on IRC had a pretty similar problem to you today. Eventually we found out it was a corrupt/damaged user profile. rm -rf .mozilla/frirefox deleted all the profiles under the users account and forced firefox to make a fresh profile, this fixed the problem.
You mentioned new user profiles don't have the same problem. To me that suggests it's deffinatly a borked profile. If you decide to rm the damaged profile and it work's, make sure you tell us about it on here so I can close the bug. Note: Deleteing the profile will cause you to lose any specific configuration and bookmarks etc. -- Firefox address bar and "undo close tab" problem https://bugs.launchpad.net/bugs/283961 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs