Unable to remove mapped drives.

I have a client who uses his home computer for work.  In the past he has connected to the office via VPN and has had mapped drives for the server at the office.  The server has been replaced and the drive mappings changed, however I am unable to remove the old map drives from MyComputer on his machine.  When I attempt to remove them by right-clicking, using Tools-Disconnect, or using net use x: /delete from the cmd prompt, I am presented with the same error; The network connection could not be found.