Error:Your account is configured to prevent you from using this computer

give them a new username and password, and assign appropriate levels of access.
Any data in the old user profile may be copied by the admin to the new users' folder,
but since there is a possibility of profile corruption it would be best to not over-write
the newly created user folders. Copy the data in to folder named something like
"old-username", Once the new user logs in, they can pick what they need to keep
from that old name. Anything not wanted can be deleted.

i would check and see if the user is restricted to one PC in Active Directory. That is the only time that I've seen this happen. Has the name of the PC been changed? That would cause the issue if the user in AD is only allowed to log into a certain named PC.