Today I saw in the update-list of Feisty (the auto-updater) that Thunderbird had some new stuff. Some time ago (two weeks, not sure about that) Ubuntu‘s repositories finally had Thunderbird 2.0.x and I already upgraded. For some reason the new version did not pick up my mail-files I was using with a manually installed 2.0, so when starting Thunderbird, I managed via symbolic-links that MY version was started, not Ubuntu’s. Now the auto-updater installed the newer binaries, and after restarting Thunderbird I found myself looking at old mail. Darn.
After some puzzling, I found that my version was using mail-files in ~/.thunderbird, whereas the Ubuntu-version used ~/.mozilla-thunderbird. Copying files from one to the other was what solved the problem.
Oh, I created a backup this time 😉 After I got things in working condition of course.