When a Windows XP user can't login because of the following error message: "Error Message: Your Interactive Logon Privilege Has Been Disabled. Please Contact Your System Administrator", then try the following steps:
"To configure a user account to be unable to log on to any terminal server, follow these steps:
On the domain controller, start Active Directory Users and Computers.
Right-click the user account, and then click Properties.
Click the Terminal Services Profile tab.
Click to select the Deny this user permissions to log on to any Terminal Server check box. Or, click to clear the Allow this user to log on to any Terminal Server check box."