Yeah, that is very intriguing - normally 'switching' ACPI results in what i happening to you without the switch.
As for VHD support, my apologies, last time I looked they only supported OpenVHD, and I have forgotten to go back an see what they support now - but it is nice to know they support VPC VHDs - that means that I can download some existing VHDs and load them in VBox - yay!
Getting back to your issue, though, even after installing the
drivers and such, enabling it causes the VHDs to hang?
I think it is partially b/c the Hyper-V may still not support Virtualization as well as VBox, but that was not my understanding when I was researching it for the university....
Let me look into it again....