Drive mappings are shown as not connected, display a red "X"

Drive mappings are shown as not connected. Viewing the drives under My Computer shows a red X under the drive.
Mapped drives become disconnected at random intervals, up to days after machine is booted.
Slow mapping drives.
Mapped drives become disconnected when copying files.
Mapped drives become disconnected as soon as login script execution completes and desktop is available.
Server retains multiple unused connections for each user.
Servers have not been rebooted for a long time.

Reboot the Novell NetWare 6.5 server.

LAN trace shows the server unexpectedly tearing down the active NCP connection with the workstation. The workstation makes a new connection, but the drive mappings don't belong to that connection, so they are not re-established. Enabling "set console display watchdog logouts on" shows that the watchdog mechanism is not what is causing the connections to be removed.

Possibly a 3rd party server application, such as a virus scanner may play a a role in the problem.