Exchange 2010 with TMG - OWA Expired Password issue

When we setup a new user account, we check the box under account setting "use must change password at next logon"  The problem is when the user logs on to a computer with a generic account and then tries to log in to OWA for the first time, they get

You could not be logged on to Forefront TMG. Make sure that your domain name, user name, and password are correct, and then try again. If we remove the the check from the account setup they login just fine. Anyone know where the issue could be.   Thanks