[Dovecot] invalid mbox

[Marc Lucke]

dovecot-1.0-1.1.rc15.fc6

When I attempt to drag spam from one IMAP box to another it tells me 
that I have an invalid mbox format for some emails.  Occasionally too 
when I click on that email box it gives me the same error.  uw-imapd 
never gave me those problems.

I use Thunderbird 1.5.0.10 and have the same problem on Windoze XP and 
MacOSX.

Can I and how do I solve this problem?


Marc