Fixing Weird Behavior after Thunderbird and Mozilla Upgrades
FreeBSD 5.3 RELEASE shipped with thunderbird-0.7.3_1.tbz and firefox-0.9.3_1.tbz. Newer precompiled packages are available, so I upgraded to thunderbird-0.9_2 and firefox-1.0,1.
When I started Thunderbird, I found I had no mail in any of my folders. My default folder languages had also changed to Arabic. After searching the Web, I found this forum which suggested deleting the compreg.dat file in the .thunderbird/default.XXX directory. Sure enough, after renaming the file, a restarted Thunderbird performed as it should have.
When I started Firefox, I found that middle-clicking on links launched a new, yet empty, tab. I also couldn't use my arrow keys to navigate the address bar. I decided to move the compreg.dat file in the .mozilla/firefox/default.XXX directory. After restarting Firefox, it too worked fine.