Have you tried resetting the PRAM. It goes a long way to fix hardware problems. My Pro was hanging almost every shutdown after installing 10.6 (sitting there with nothing but the desktop background and never shutting down). So I did the PRAM reset and it hasn't happened since.
Hold Command + Option + P + R until you here the bong a second time.
Hold Command + Option + P + R until you here the bong a second time.