user can’t login to domain

I am running Window Server 2003 with Active directory setup. I have XP computers that is connected to this domain. One user cannot login to the domain, it says “the user profile cannot be loaded”. I looked at the properties of the user and I saw that it was a Domain User(which is what its supposed to be). So just for fun I made the user a Domain Admin and they were able to login. Of course I dont want them to have admin rights, so is this a domain user problem or something else? if this is confusing I will give more info if needed. Thanks