That's a pisser. I did the FF3 update a while ago with no problems (knock on wood). For FF users, and Thunderbird as well, Google Mozbackup, it's a great little free program that backs up both programs. In FF it gets all your bookmarks as well as your settings and such. For T-bird, it saves all your emails and account settings, etc. Then if you need it, just open Moz, click restore, and you're done. The handy thing is, it makes it super easy if you change computers....just do a basic install of FF, T-bird, and Mozbackup, then do the backup files on old PC using Moz saving to a flash drive, then just restore on the new PC. All your settings and everything come over in a matter of seconds, no messing around with pop, SMTP, passwords, nothing. Also brings over your add-ons, plug-ins, etc. I love it. I backup every week, takes seconds.