Problem giving domain group permission

Please help! I am having problems giving domain groups permission to anything in XP Pro. I am trying to add a domain group to the local administrators group. I am also trying to give a domain group permission to a folder on a network drive. Each time, mmc crashes after I enter the name of the domain group and click the OK button. From the event viewer:

Faulting application explorer.exe, version 6.0.2800.1106, faulting module netapi32.dll, version 5.1.2600.1106, fault address 0x00024e14.

The application, C:\WINDOWS\system32\mmc.exe, generated an application error The error occurred on 08/04/2003 @ 10:52:56.764 The exception generated was c0000005 at address 71C44E14 (NETAPI32!NetUserGetLocalGroups)

The domain is NT 4 and my computer is running XP Pro SP1.