After updating the servers to Zen for Desktops 7.1 and to updating the
client machines (XP SP2, NW 4.91 SP2 client) as a test from the ZFD 7
client to the ZFD 7.1 client NALDESK fails to start.

The symptoms are that the NALDESK icon flashes in the system tray then
disappears. No errors are seen in the event viewer and NALDiag fails to
run with a message "Cannot create Nal engine" so I cannot change the
logging for the zen client.

I have tried getting rid of AV software.
The Novell services all seem to have started correctly.
Removing and redeploying on multiple test PCs - with the same result.
Deploying without the mirror driver.

Anyone got any good ideas?