I think that when you have the kind of problems you have, if you get it running you should definitely NOT overclock it the first thing you do. Take it easy and run it at standard speed for a few hours. Shut it off/Reboot it a couple of times, and when you are sure everything is working perfectly, THEN you could proceed with overclocking.
Now, my suggestion is that you hardware-clear CMOS, and take everything from the beginning...