I upgraded some machines to XP SP3, and now whenever the user tries to install anything they get a "You must be an administrator" dialog box; however I went in locally and added the user as part of the Administrator's group to the local computer's Users and Groups (i.e. Admin Tools -> Computer Management -> Local Users and Groups). The user has standard rights on the domain but nothing that would block this; users on SP2 don't have this problem and can install software.
How do I go about fixing this? It's getting annoying for the users to have to call me over and then have to log out, then log back in as the local Administrator account in order to install anything or configure an IP printer (option is grayed out except with Administrator account).