If I load mozilla mail and then use another mail program, like mutt for example, and the contents of the mailbox have changed, then mozilla gets confused about the actual state of the inbox and clicking on a message will show the contents of another message. The state can only be restored by shutting down mozilla and deleting the INBOX.msf file.
Can you attach a mozilla protocol log, and also say what build you're using? http://www.mozilla.org/quality/mailnews/mail-troubleshoot.html#imap this would be an imap problem, not a mail database problem.
what build are you using?
I was using 0.9.9+ 20020318 when I reported this. I have since upgraded to a recent 1.0+ build and the problem seems to have been resolved.
marking wfm then, thx.