[Dovecot] IMAP FILE MOVE ERROR

[agreig at protectionprojects.co.za]

I recently installed dovecot.x86_64 1.0-0.beta8.1.fc5 on a new server.

Our network users use Pegasus as their mail readers, accessing their home 
folder on the server via Samba. Each user has a pop3 set of folders, and 
we have a shared imap set of folders. This has worked very well for 
previous versions of dovecot.

When moving files between folders on the imap set, we get an error 
message from Pegasus, as follows: "The IMAP server that manages this 
mailbox or folder has reported an error during the operation you have 
attempted to perform."

The operation cannot be completed."

Operation of the imap INBOX only restores once it is "refreshed" via 
Pegasus.

The maillog shows the following message for this error:
"dovecot: IMAP(tekstaff): file mail-cache-transaction.c: line 709 
(mail_cache_add): assertion failed: (fixed_size == (unsigned int)-1 || 
fixed_size == data_size)"

A search using find / -name mail-cache-transaction.c does not find such 
file.

I am stumped. Any help to fix this will be much appreciated.