User Lost Admin Rights

W2K SBS; W2K clients: I have a user that has always been a part of the Admin group. For some reason, he no longer has the capability of doing Admin duties. When logged in as him, it keeps telling him he does not have sufficient rights and needs to be a part of the Admin group to perform those duties. I don’t really want to blow away his user ID and recreate it. I have removed him from the Admin group and put him back in. I have copied his ID and it does the same thing. It is only happening to him. Why did this happen, and how can I fix it? Thanks!