Something happened to my mail on Thunderbird (Mac v2.0.0.17) such that the profile was corrupted. After reading a lot of self-repair entries, this problem seems common.
1. I backed up all my old mail, saved separately 2. Then created a new default profile via the profile manager 3. I then bulk copied all my original files except pref.js into the top folder in /Users/me/Thunderbird 4. But nothing appears. So I recreated at least one mail account but again no old folders are being shown
Thunderbird was kind of stupid about it last time I had to do that. I remember having to tweak the .pfs file with the correct paths to get an existing install to see the new directories. It was too long ago to tell you what I did though.
For the IMAP account you should be able to give it your settings and it will be done.
OH wao, I missed that you were on a mac. Yea, on a PC you just drag and drop the backup folder and it magically works. My brain hasn't been in the right place this weekend. Apologies.