Error message when you try to map to a network drive of a DFS share by using a different user name than the one that you used to log on to Windows Vista: “A specified logon session does not exist. It may already have been terminated.”
You log on to your Windows Vista desktop computer by using your regular domain account. When use other credentials to map to a Distributed File System (DFS) share, you receive the following error message:
ERROR_NO_SUCH_LOGON_SESSION winerror. A specified logon session does not exist. It may already have been terminated.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB968264.