windows server 2003 issue with automatic update problems

i am trying to solve a problem with win2003 server. I have this business that has several computers with 1 domain controller and several domain users. but on the individual work stations(xp Pro) that are domain users the automatic update will download but will not allow to be installed.

Is this a problem with the domain controller or users?? or with the group policies for the users

Does anyone have any solutions to assist me in solving this problem???