I have the same problem.
I have about 130 machines in my network and this problem appears when i upgrade my windows 2000 prof. system to windows xp prof. SP2.
I saw my configuration in \"Local security settings\" and it is correct, in
Classic mode.
However, i can not modify this option...

This computer is in domain, but the user is administrator of the domain, and in this computer.
Any other idea?
Thank you very much.
Juan Moreno.