Remote Desktop Connection Error Message

Both machines running Windows XP Pro. I use my desktop to remote access our email server, and have been doing this for well over a year without any problems. (I also use my desktop to remote access the file server, running Windows Server 2003 and it is working fine.) Nothing has changed, but about a month or so ago, I began getting this message when trying to remote access the email server:

The system could not log you on. The server authenticating you reported an error (0xC00000BB). You can find further details in the event log. Please report this error to the System Administrator.

Also, when I try to physically log on to the email server, I get the same message. (Which was terribly frightening the first time it happened!) Once I reboot, however, I can log on just fine. I can also remote access immedately after a reboot. But not for long.

I've googled it, and everything I've found refers to using a Smart Card. I don't use a smart card.

I've tried adding a different adminstrator account to the email server; deleting the original administrator account; changing access controls; trying to remote access from a different computer - nothing works.

Any suggestions?

 

pleae post the error message in the system event log so we can perform queries on it.

 

It may be that I'm an idiot, but I don't see an error message in the system event log. I've checked the remote machine (the email server), and I can find the popup message telling me there were other users logged on to that computer that I got when I shut down the machine using the power button (because it wouldn't let me log on to shut it down correctly), but that's it.

There are a couple of error messages that "The IMail IMAP4 Server service terminated unexpectedly." Followed by the message "The IMail IMAP4 Server service entered the running state."

I've also checked the system event log of my desktop computer, and there are no error messages at all.

Did I miss something?