Did you have any luck? Things like this bug the crud out of me, it's good it's not my system, I would've been up all night debugging, and ticked off the family;-]
How about when you use powercfg /getactivescheme, it's linked to a good (valid, with sleep states) scheme?
What happens when you use the sleep button, or the power menu item, and select sleep and/or hibernate, does that work?
I don't think I ever asked this before, but if it can't enter a state, due to a request or similar, the event viewer should show it. If this is the case (it won't go to sleep or hibernate at all), my trick of setting the (sleep/hibernate timeouts to 1/2 minutes respectively, should help. From there, look at the event-viewer, after 135 seconds or so, and you can typically see what gets registered, in terms of error or warning events, for power (you can filter on power events, but usually just a glance and some clicks does it).
The event viewer can really be useful here, if it can go to sleep manually, but just fails to automatically put itself
I'm glad you appreciate my help/attempts, wish we were actually getting closer to solving it (which is possible, usually it's one thing that does it) though ;-]