Sorry for the triple post, but now I have a little breakthhrough regarding the 12" PB.

The thing died on me just now, so I decided to take off the palm rest and poke a little more around the motherboard, and I found this:

If I apply pressure to the left side of the DC board connector, the machine boots.. AHA, bad connections to the motherboard from the DC board. I'll see what I can do to remedy this.