Bake normal map hang/crash

Hi, I am new to Blender. I have been following David Ward’s Johnny Blender 2.0 series on youtube and at part 9 I cannot proceed past the baking stage. Here’s my problem/s:

With 3 subdivisions in Multires I can bake fine without crashing.
With 4 subdivisions Blender will chew up all my RAM instantly and CPU usage will go down to 0 after a while. Eventually it will “give up” baking and just display a black image in my UV window.

I have tried both Blender 2.57a and b, 64 bit only so far. I started with 2GB RAM then tried upgrading to 4GB but the problem remains.

My specs:

CPU: Intel e2140 1.6GHz dual core
GPU: nVidia 8800 GTS 640MB
OS: Windows 7 64bit

Thanks for any tips you might have.

it might help to apply the multires modifier before baking.
if you want to keep it you can save beforehand, then bake, save the baked result and reload the blend file.

hope that helps