I sort of understood the problem, just wanted to know the other answers. If you can hit F8 and get into Safe Mode during the boot, you might be able to determine if it is a driver causing the problem.
When you just restart, all of the memory is not cleaned out, so something left may be causing the problem, or a driver. If you do a cold boot instead of a restart, does it boot normally?[after a cold boot it starts normally]