NT4 Server not booting from SCSI

[Guest_imported]

One of our NT4 Servers will not boot from a SCSI HD, SCSI BIOS is enabled and drives initalise okay, after that just get a black screen with flashing cursor in the top left corner!
Boots okay from a floppy disk even though the boot.ini/ntldr/bootsect.dos/ntdetect.com files are identical!
Any suggestions? I'm thinking maybe the OS hasn't got the SCSI drives (Ultra160) loaded, how would I add them at this stage given the OS is installed already?
Tried the BCUPDATE program to no avail!!!

Thanks.

 

[BOKA]

How big is your system partition? Does this box have the same config as the rest of the pack?
Is there a possibility of a plain old bootsector virus?