[Dovecot] problem with dovecot and thunderbird while deleting

Hello!

I have very strange problem with dovecot and thunderbird while deleting messages. The problem is that they are not actually deleted from storage filesystem and if I later run mutt I can perfectly see them, though marked with 'D', so mutt ask to delete them on exit and this time they dissapear from filesystem. I enabled in thunderbird 'remove it iimediately' feature, but this doesn't help. When I delete message from mutt it removed from filesystem just fine.

IMAP server: OS: FreeBSD 6.1p2 dovecot: dovecot-1.0.b9

Client: OS: Debian sarge Thunderbird: thunderbird 1.5.0.4 (from backports.org)

Any suggestions ?