This error can occur if the drive letter you are mapping with a net use command is already mapped in the user's properties.
NOTE: Open a CMD prompt and type net helpmsg 85.
Home drive mapping is processed before the logon script runs. If the home drive maps the drive letter successfully, the logon script fails because the The local device name is already in use.
To fix the problem, change the drive letter mapping in the logon script or in the home drive.