[Dovecot] MIME structure intermittently lost

I'm using Dovecot-0.99.10.5-0.FC2 on Fedora Core 2 on the server, and Mulberry 3.1.6 over Win2kSP4 on the client. Intermittently messages with multiple parts show up as a single text part. I'm not sure if it's Mulberry or Dovecot. I just turned on IMAP logging and restarted Mulberry and a message with two text/plain parts that wasn't showing the 2nd part is now displaying it correctly. I hate heisenbugs!