I don’t know if this is any help to you now, but someone else may benefit:
I was getting GRUB errors with DelFX710 thin clients running Windows 7 WES (window Embedded). These thins had the most recent updates applied and would be unbootable. I found some fresh out of the box without the updates (same thin client hardware). Perfect images no problem. The defining difference (I think) is that the non-updated ones used GRUB 1.5. The new ones GRUB 2.
For what its worth.
cheers