Problems with UV and Ambient Occlusion Mapping

Recently I started modeling a dragon, following a tutorial by David Ward on Blender Cookie. It should be noted that this is my first attempt at seriously using Blender. When I reached the UV mapping and Ambient Occlusion mapping sections of this tutorial:

I could not continue, as whenever I attempted to bake something it would never finish. Each time it would stop baking approximately one third of the way through, and large triangles would begin to appear and eventually completely cover the preview of the map. I had followed the tutorial exactly, so I don’t know what the problem could be. This happened with both UV and Ambient Occlusion maps. Can anyone help?

How much RAM does your machine have?

Currently, 4 GB.

As it’s been some time since the last post here and my problem still has not been resolved, I’ll go ahead and bump this. Does anyone know how to fix this? And does it have something to do with my RAM?