I have a new Dell T-610 2008 R2 Hyper-V that has 1 2003R2 x86 virtual machine. The 2003 vm "locks-up" or "freezes" a couple of times a day. I have to restart the entire server or "force" a shutdown of the VM. The VM is set to automatically restart and autmatically startup after reboot, it does not. The event viewer on the 2008 server shows no critical errors on or around the time of the lock-up. The 2003 event viewer has a single critical error stating that "The previous shutdown at xx:xx am\pm was unexpected". I have been looking at the events on or around that time and seem to notice a number of vss writer informational message on the 2008 server. I disabled the 2008 Hyper-V backup and the problem seemed to have stopped. Yesterday, after a manual 2008 backup I setup a 2003 reoccuring backup within the VM itself. This morning I had the same problem, the VM was again unresponsive. It seems like a 2003 Shadow Copy issue or a 2008 VSS-Writer issue but I am not certain.
note: I have installed the hyper-v backup update and registry modifications allowing for 2008 R2 VM backups. It was rigth after that modification that I began to have this issue.