proliferation of messages on first sync

[Paul <lists@xxxxxxxx>]

Hi -

I just ran Offlineimap 6.0.3 (the Ubuntu Intrepid packaged version) for 
the first time, to sync my local laptop with my remote IMAP inbox, which 
is hosted on a stock installation of Dovecot 1.0.3.

There were 771 messages in the remote inbox when I started Offlineimap 
and went to bed. In the morning, Offlineimap was still running, but it 
had duplicated the messages in the inbox multiple times. When I stopped 
the process, there were 2268 messages in both the local and remote 
inboxes, and it was continuing to add messages.

I didn't see any error notifications, and my .offlineimaprc file is 
pretty close to the minimal version.

Surely I'm doing something wrong. Where should I look to figure out what 
it is?

thanks,
        Paul