There is no reason for that really. Sounds like a bad or corrupted profile to me. Try rebooting, log in as admin, go to C:\Documents and Settings. Locate the profile name that the keyboard does not work under. Rename it to .old. For example, if the profile name were jsmith, you would rename the profile folder to jsmith.old. Log back in as the user. Does the keyboard work? If it does let me know and I will tell you how to copy all of your files/favorites from the old profile into the new one.
