Windows clients will not log off when hours expire.

I have a Windows 2003 domain with Win XP SP2 clients. I have set a domain policy to log the workstations off when user logon hours expire. I have not been able to get this to work. I have verified that the client is receiving the policy settings and all other restrictions are taking effect. I have done some research online with M$ and they have a hot fix for it but you have to call for technical support before they will give you the fix. Has anyone else encountered this and have a way around it?