Disk not found, 'System Halted!'

I have just installed Safeguard 5.50 for a client, and after the initial reboot I get:

Sophos Safeguard is starting.

Please Wait ...

Cant work out which disk we are booting from.

Guessed BIOS device 0xffffffff not found by probes, defaulting to disk0:

cant loads 'kernel'

Safeguard Base Encryption could not be started.

System Halted!

If i reinstall windows, that boots fine. There are no hardware problems that Windows reports. With Sophos giving this message i cant use any of the hotkeys to test with. Windows and Sophos are both instaled on Disk0 (C) so it should be fine   :( .

I have never seen this message before...any help appreciated!

thanks

CHRIS