I'll try to pack up what I've got so far.
And I made a mistake in my earlier post. My PC has 1 GB of RAM and a 224 MB graphics card.
Watching with the task manager open, the compiler was taking 45-65% of the CPU usage during lightmapping. I'm not sure if this is part of the problem. Took 1716 seconds for a simple build.
Level.zip Just recall that the level isn't finished, skins and textures aren't final and are for the most part temporary.