Several Windows Updates fail on AD-domain member systems

I think this might be a group policy issue as I have exhausted every other
suggestion to fix failed updates that I have found in this newsgroup and
elsewhere.

I have several Windows XP and Windows 2000 Pro & Server systems which refuse
to install a number of pre-SP2 updates. One particular XP system fails to
install: KB842773, KB840315, KB841873, KB839643, KB840374, and KB835732. If I
download these updates and try to install them manually they fail, even in
safe mode. All but KB835732 give there error message: "You do not have
permission to update Windows XP. Please contact your system administrator."
This is while logged in as the local administrator. KB835732 fails with the
error: Setup could not backup registry key
HKLM\SYSTEM\CurrentControlSet\Control\Nls\MUILangu ages\RC\rtcdll.dll to file
C:\Windows\$NtUninstallKB835732$\reg00003. 1314: A required privilege is not
held by the client."

The only systems I have been able to install these updates on are ones that
are not domain members which leads me to believe this is a GP issue but I
have no idea what setting could result in this.