mail authentication

Running RC4, mail authentication to a Uwash IMAP server does not 
work. RC3 authenticated properly to the same IMAP server. I get the 
following log entry on the IMAP server:
Jul 27 16:41:02 gbmail imapd[19801]: Command stream end of file, while 
reading line user=??? host=UNKNOWN
I am able to authenticate using a Cyrus IMAP server, but all of my user 
accounts are on the Uwash box.
Thanks,
Alan