Claus Neilsen (PowerShell pro) posted an alert on the Minasi Forum this morning regarding an issue where Windows Server 2008 R2 can blue screen if the Hyper-V role is enabled on HP Servers. Claus reports that “the fix he has found so far is disable Intel Core C3 State option in the BIOS”.
EDIT #1:
There is a hotfix that will probably fix this issue. KB974598 refers to when "You receive a "Stop 0x0000007E" error on the first restart after you enable Hyper-V on a Windows Server 2008 R2-based computer". It goes on to say "This problem occurs because the system uses a C-state that is supported by the processor. However, the C-stateis not supported by Hyper-V". This problem is not specific to HP computers.
Thank goodness for Google and this post! I would never have figured that one out.