How to fix intermittent blue screen of death?

This is a 15" MacBook Pro that came loaded with 10.6.7. 2GHz Intel Core i7, 4GB 1333 MHz DDR3. Getting a blue screen on startup. Sometimes (1/10 times) it will boot okay. Cannot startup on the DVD (holding down the C key). Just will not work. Verified the DVD drive does work as I was able to get the hardware test to work on the other DVD (hold down the D key). Tried using an external drive with same failure. It is currently up and running. I ran the Verify Disk and it did not find any issues. Then I ran Verify Disk Permissions and it did find some problems with usr/lib/libruby.2.0... and usr/lib/libruby.dyllb. Few other issues with Safari, Printers and iBook.app. It is repairing permissions as I type. I fear the issue will not be resolved by this. I have a Time Machine backup on a USB drive. That's all I can think of to write. Any suggestions on how to cure the blue screen issue on startup?