I found this article very helpful as it taught me a lot about Vista.
But it missed the cause of my problem (easy to happen with so many things to consider and different hardware manufacturers)
My I suggest an additional step 1 point:
Check mother board switches!
My Asus PK5PL-CM has a jumper that sets different sleep voltages for USB.
One for S1 sleep and another for S3 sleep

dah - should have read the mboard manual a bit more carefully. When I changed the jumper to S3 my Vista Sleep/Restart problem was solved.