I am receiving the following error in Hyper-V 2012 (RTM build):

Hypervisor processor startup failed (APIC ID 0x6, status 0x1035).   Further processors in the system were not started.

• I had no issues with Hyper-V in Win 2k8 R2
• I'm running the 2.7.0 bios
• CPUs show up in device manager, but 

More detail can be found here: http://social.technet.microsoft.com/Forums/en-US/winserver8gen/thread/ac75a2b0-d8b9-4347-9c8e-12592a0b2b9d