Windows 2000 Domain members cannot update via Windows Update

Hey all, since the middle of this month my Windows 2000 servers/clients
cannot update via Windows Update. All my XP clients work fine. There seems to
be a security policy setting that is blocking this functionality but cannot
determine what it is. I come to this conclusion due to the fact that if I log
onto a server as a local administrator as opposed to the domain, they can
access and update successfully. This is not an option for my domain
controllers though. Here are some of the things that I have tried.

- By passing Proxy server
- Added http://*.update.microsoft.com; https://*.update.microsoft.com;
http://download.windowsupdate.com as trusted sites. Thus eliminating the
Proxy server as a potential cause.
- Most the suggestions on Windows Update troubleshooter
- Removing guest from any user groups
- This occurs on mulitple subnets

If anyone has any suggestions as to what security policy/group policy would
cause this behavior, it is much appreciated.