[Dovecot] Occasional error msgs from 1.0-test49

I'm running 1.0-test49 on Solaris 2.8. MUA is Thunderbird (or mutt) running on FreeBSD. I'm using Maildir boxes.

Occasionally, when browsing new mail in INBOX, I get an error back from the imapd, displayed in Thunderbird as the following popup msg:

The current command did not succeed.  The mail server responded: 
Error in IMAP command UID: Invalid BODY[..] parameter: 
Missing '>' in '<36864,-34800>'.

From this point, nothing much works reliably until I quit the MUA and start again. Sometimes, if I keep working, the email that was being fetched is shown but is corrupted and the msg body contains another copy of the whole email (header & body), sometimes 2 extra copies.

Nothing is in the maillog.

This _didn't_ happen with 0.99.