Login Problem in OWA on SBS2003

I have some accounts (not all) that can’t log into OWA on SBS2003 for some reason. Nothing changes on the server yet I receive an error on OWA that says “You could not be logged on to Outlook Web Access. Ensure that your user name and password are correct, and then try again.” The only way I know to get things working again is to create another account and kill the old one. Problems is that I have to dump the email. Ug.

Thanks for your help!