A 2008 server with the Hyper-V role sometimes hangs at  Shutting Down and a power cycle is required to restart it.   This appears to occur with some servers due to BIOS incompatability, have read on some forums that upgrading to lastest motherboard BIOS has resolved issue.

Personally had this happen on servers fitted with Supermicro X7DWU motherboards, problem continues after lastest BIOS installed running Windows 2008 SP2 and all relevant patches.

This is a real pain when remote booting servers as they never come back online.

No shutdown issues on HP ML350 G5 and  HP XW4600 worksation in my test environment.

Maybe Microsoft will bring out a patch !