[Dovecot] deleted messages not going away in Thunderbird?

Hi folks. This may be a dumb question, but I can't seem to find a clue.

I'm running Dovecot v1.2.9 and Thunderbird v3.1.7. If I delete messages using a different IMAP client (I also use an iPhone and occasionally SquirrelMail), I would expect those messages to disappear from Thunderbird the next time I start it or click on "Get Mail". In fact, they do...most of the time. Sometimes, however, they just stick around. If I do a "Repair Folder" on the inbox in Thunderbird, the messages go away.

Is this a known issue? My gut tells me there's some Thunderbird option to make it follow inbox contents with more "attention" but I've not been able to find it.

         Thanks,
          -Dave

-- Dave McGuire Port Charlotte, FL