Active directory user cannot create new account

This is driving me absolutely looney. I checked if he had a proxy enabled and there wasn't one. I am not suer how to run a trace on his traffic. I have confirmed several times that he is indeed logged in as himself and not the administrator, but the authentication function still insists on trying to log him in as an administrator in our other domain. The username its trying to insert based on Bruce's troubleshooting isn't even in the DB....

I figured out the problem this morning. Thank you all very much for your assistance. Basically what was happening is his machine had a cached credential for that server that it was authenticating with in leiu of his own credentials. Here is a brief description of what I did to resolve it: