DISK BOOT FAILURE but can still boot! (weird)

This is a problem I’ve never come across before. I’ve seen hundreds of DISK BOOT FAILURES in my time, but this one takes the cake.

When I power on, POST checks OK, the HD and DVD drive are found OK, then I get DISK BOOT FAILURE…

Here’s the strange part, it boots up when I press ENTER.

Boot order is:-

Hard Disk
Disabled
Disabled

I have no Floppy Drive. There is no CD/DVD in the DVD Drive.

WinXP Pro is on the HD and runs fine.

Any ideas as to what could cause this?

nForce3 MOBO
FUJITSU IDE HD (set as Cable Select otherwise it doesn’t get past the boot failure)

Thanks in advance,
Matt