[Dovecot] Log Message Disconnected: Disconnected

[Jackie Hunt]

We just started running Dovecot this summer at our campus.
Overall things have gone very well, and performance have
improved since moving off of U of Wash.

We have run into an issue with a user running Thunderbird 
2.0.0.6 on Solaris.  He is seeing a very long response time (20mins+)
on his first mailbox selection each morning when he comes into 
work. 

I looked at the Dovecot log, and the only think I can see that
might be a bit out of the ordinary is two Disconnected messages
that happen about 30 minutes apart each morning:

Aug 17 04:54:08 host dovecot: IMAP(uname): Disconnected: Disconnected
Aug 17 05:24:09 host dovecot: IMAP(uname): Disconnected: Disconnected

The disconnected messages for other users say "Disconnected: Logged Out".
I don't know for sure if these messages are related to his problem.  
Can anyone can shed some light on why Dovecot might indicate a "double
disconnect"?  

Thanks,
Jackie
---
Jackie Hunt                                                       
ACNS                                    Voice:  (970) 663-3789     
Colorado State University               FAX:    (970) 491-1958
Fort Collins, CO  80523                 Email:  jackie.hunt at colostate.edu