no admin rights logging onto 2k domain

Hi,

Got a strange problem just now, a windows2000 server as a pdc, with several 2000 pro workstations, all users can logon to the domain just fine, BUT, they only have “user” rights, when I add a user to administrators group in active directory, it just doesnt seem to pickup that the user should now have admin rights, this is causing major problems as I now have to go around loggin in as admin everywhre in order to do things! has anyone any suggestions?
(all running sp2)
TIA

CALV