Time out error

[NEXCOMPAC]

I am trying to add a user to the power user group on a particular machine running windows xp pro. We have active directory running on win 2k3. I signed in as an admin and went to computer management users/groups. Under groups, powerusers I double clicked, then selected add. I browsed the directory selected the user, clicked check names, then it just hung... The error message I got back was
"SELECT USERS, COMPUTERS, AND GROUPS
Windows cannot process the object with the name "Tina Hodges" because of the following error:
The RPC server is unavailable."

I came accross this problem due to the fact that this user today was not able to log onto quickbooks due to the message "You must be part of the Admin or Power User group to run quickbooks." She was in quickbooks yesterday! So, now im confussed. Any help would be great. Thanks.

 

[NEXCOMPAC]

Ok, two things i found out. If I remove AVG 7.1, things started to work much better, however there was still some residual effect in active directory so I created a new user and then after AVG was gone, I was able to add her to powerusers. Go figure...