Snow Leopard Server Mail disables access

This has been an intermitten problem for over a year. Every once in a while multiple email accounts in the "Workgroup Manager: local" loose their check mark next to "access account".

On the client machine, the first indication that something is wrong is when the client (me) gets an error message saying the password does not work.

This is on a Mac Mini colocated in Florida. I have 3 IP addresses and the emails work except when this crazy thing de-accesses.

It happens to email accounts on any of the 3 IP's. There are no mail quota's set and they are all set for both POP and IMAP.

I can't add anyone else until this is fixed. I'm using 10.6.8 Mac OS X Server.