XP log off error

We have 2 Windows 2000 DCs, and 1 NT server, our workstations are a mix of XP, 2000 professional and 98. There are about 65 workstations mixed betweend laptops and desktops. The problem is one desktop that XP Professional installed will not let the user log off, if the administrator account is logged in there is no problem and even if another user logs on they will be able to log off. I have checked all the local, and domain security policies as well as all permissions and group memberships andhave found no difference between this user and anyone else on the network.

Any ideas are greatly appreciated.