I've tried upgrading from test-51 to test-68, with mixed results.

It seems to fix the problem I had with imap and Thunderbird getting confused and not showing headers or body for some email.

But something in dovecot is coredumping when I select certain mailboxes. Thunderbird just hangs when you select that mailbox, and mutt gets an EOF on the imap socket while "fetching message headers".
Other mailboxes seem to run OK. The failing ones _might_ be empty or have only 1 message in them. Removing index files doesn't help.

There is a core file in /var/run/dovecot, and file(1) says it's from dovecot-auth, but GDB can't make sense of the core with that executable, and the login has well and truly run when the core happens.

(The core doesn't seem to be from the imap process either.)

Any clues how I might debug this?

[Solaris 2.8, gcc-3.3, dovecot test-68, imap+Maildir, Thunderbird 1.0.2 on OSX and mutt on Solaris]