Oh so the users are pre-2008 users? If you create a new user in 2008 does it work right? There is a lot of stuff that can be wrong, but usually its permissions, look at this thread, too many tips on what to check/try to list them all here, but i am sure the one or other thing could fix your problem:
http://social.technet.microsoft.com/Forums/en-US/winservergen/thread/2e3d27cf-38ec-433d-8bee-2a69a73871a5