I recently installed the upgrade to Thunderbird 3.0 on our main PC. In my account, all was fine afterwards, but my wife had a very strange problem: All previously stored passwords seemed lost. TB 3.0 asked for the passwords of all accounts that she had, both IMAP and NNTP. When I started TB 2.0 (which I reinstalled for investigating this issue), all was fine again — apart from the password for the NNTP account, which was incorrect or missing, so I entered it again.
I noticed that now that TB 3.0 was installed, there was a file
signons.sqlite in the
Profiles folder in addition to the well-known
signons3.txt file. I figured that the SQLite file was probably the new password store, which was migrated from the pre-3.0 password store in the TXT file. I further figured that during the migration something probably went wrong (eventually the missing/incorrect/corrupt NNTP password?), so I removed the SQLite file and started TB 3.0 up again. Upon starting up, it recreated the SQLite file, and this time all worked well.
So, if you folks have a similar problem, try the approach I described here. It should not be risky at all, since the TXT will always be the “master” file when migrating from 2.0 to 3.0, so removing the SQLite file will have it re-created again upon next startup.