Unknown Crashing of Hyper-V host

I already had a thread with this question in the Windows group but it's pretty much dead now,

EDIT: here's the link to the other thread http://community.spiceworks.com/topic/295361-random-crashing-of-hyper-v-host?page=1#entry-1939003

I have got an Acer Gateway GR380F1 with a single Nehalem CPU and 12GB of RAM, I'm trying to host virtual servers on it, the host OS was 2008R2 and I've now rebuilt it with 2012, I've got a problem with it randomly crashing every so often, the host along with the VMs locks up, I've ran the usual battery of tests (memtest86, various HD tests inc hdtach, prime95) on the hardware and it's all fine.

The only thing I have to go on is the event log, which stops recording events from the time it locked up until it reboots. In this case 22/02 @ 8:00 until I just rebooted it 25/02 ~8:50. The issue occurs on 2008R2 and 2012, I've tried different AV products as well.

Any help? I'm really stuck and I need this in production asap.