Windows Server 2003 reboots at logon screen after service pack install

Hi guys,

I've got an installtion of Windows Server 2003 on an HP DL360 with 2GB RAM running Citrix.

It had no service packs installed, so I have tried to put on SP2. The installtion seems to complete successfully and asks to reboot at the end. Once the box has rebooted, as soon as you hit Ctrl+Alt+Delete, the box reboots. It will keep doing this everytime you try log on. Windows is on a mirrored pair, so I've rebuilt the array a couple of times to test different cionfigurations, i.e. download SP from the web, windows updates etc. But I get the same issue through all iterations including applying SP1 first.

Looking at the eventlog the only error I can see that coincides with the reboot is this:

=================================================
Event Type:      Error
Event Source:      Application Error
Event Category:      (100)
Event ID:      1000
Date:            14/08/2007
Time:            14:13:33
User:            N/A
Description:
Faulting application , version 0.0.0.0, faulting module unknown, version 0.0.0.0, fault address 0x0006fc60.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
=======================================================

and this Dr. Watson info log

=======================================================
Event Type:      Information
Event Source:      DrWatson
Event Category:      None
Event ID:      4097
Date:            14/08/2007
Time:            14:13:33
User:            N/A
Computer:      BLACKCTX04
Description:
The application, M:\WINDOWS\system32\winlogon.exe, generated an application error The error occurred on 08/14/2007 @ 14:13:33.586 The exception generated was c000001d at address 0006FC60 (<nosymbols>)

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
================================================================


Any ideas would be greatly appreciated

TIA