[Dovecot] E-mail marked as unread

I have a problem where an e-mail will be marked as unread even though it has been read. When I click on the message the status changes to "read" however, when I go to check for new mail the status changes back to "unread."

If I move the message to the trash folder and then move it back to my inbox, the problems stops. Unfortunately, a different e-mail is affected by this problem a few minutes later.

I'm using alpha 3 on Solaris 9 and my client is Mozilla 1.7.7 on Solaris 9. No messages in the log to indicate a problem. Anybody else seen this?