After you install Windows NT 4.0 Service Pack 4 (SP4), you cannot connect to a downlevel server or share using a fully qualified domain name (FQDN) that is longer than 32 characters. The NET USE command does not work and the following error message is displayed:
system error 67: The network name cannot be found
This behavior occurs when you connect to a downlevel server and the server message block (SMB) dialect negotiated is LAN Manager 2.1 (dialect number 6).