We are commencing a rollout of NetWare Client 4.91 SP1 to upgrade our
Windows XP Professional SP1 Workstations from a previous client 4.90

We're getting a couple of machines which reboot when the screensaver
has been unlocked; when we turned off the "reboot on error" facility
from the Advanced tab of My Computer Properties, one of the machines
returned the following error

Stop: C0000021a {Fatal System Error}
The Windows Logon Process Terminated unexpectedly with a status of
0xc00000005 (0x00000000 0x00000000)
The system has been shut down.

There was no memory.dmp file created.

Our client is configured to use contextless login; adn uses the NetWare
credentials (by default) to unlock the screen;-

Any help / hints would be much appreciated

Shane C