[robgough]

Yup, worked for me. Have you ticked all the relevant options in the VM Settings?

  First stop in the System menu. Start with the Motherboard
  sub-menu and check Enable IO APIC to improve performance 
  for your virtual machine. In the Processor sub-menu check
  Enable PAE/NX (again, to boost performance). Finally under 
  the Acceleration sub-menu make sure both of the hardware 
  virtualization boxes are checked—VT-x/AMD-V and Nested 
  Paging, respectively.

- Taken from http://www.howtogeek.com/74515/how-to-test-drive-windows-8-i... (which I know is a Windows guide, but check the same settings in OS X)

[jfruh]

Hadn't seen those, will give it a shot!