When the Windows NT 4.0 user's logon script runs, they receive:
System error 1219 has occurred. The credentials supplied conflict with an existing set of credentials.
If the user's Home folder, or profile, is located on a DFS share, and the logon script maps a drive letter to that same share, they will experience this problem.
NOTE: When a logon script runs, credentials to connect to the Home folder and Profile path are stored in the MUP (Multiple UNC Provider). When the logon script maps a drive letter to this same path, a duplicate UNC path for these same credentials is generated.
To workaround this problem, change the Profile path and Home folder in the NT 4.0 user's Properties to point to the network share instead of the DFS share.