outlook express rejects login

PC running win2k on win2k domain. Problem with outlook express 6. Before today, worked fine. No new software added or changes made on machine. Today get the popup that “The server has rejected your login” with an error code of 800cccd1. The email is IMAP based, and using the same login and password as OE, can get into webmail with no problem. Even reset users password, wouldn’t poll folders (said user cancelled even though that wasn’t the case) and then gave the rejected login message again. Tried setting up email account again in OE along with internet connection wizared for LAN settings, no luck. Any ideas?