The OS was built and running fine on my SHuTTLE SH67 32GB, i7 CPU Vmware 5.1.0 box.
The moment i tried to copy a ISO (smaller files seemed to be ok) to or from the Windows 8.1 machine the entire ESXi box would PSOD.
Connecting from the *.1 to a XenServer machien to install the client tools also rendered the ESX PSOD.
Change the Windows 8.1 from using the E1000 network NIC driver to the VMXNet3. All problems gone! (for now!)