Quad core computer freezes at bios splash with a quad core processor, works with P4

Hi all,

A couple years ago, I decided to build a quad core computer. The components are as follows:

Q9550 2.83ghz processor
GIGABYTE GA-EP45-UD3P Motherboard
4GB OCZ DDR2 1066 SDRAM
700W OCZ GameXStream Powersupply
500GB Western Digital Harddrive

I assembled everything and it worked no problem for about two years until one day I decided to try overclocking. I bumped it up to 3.5ghz and it worked well for about 2 months then suddenly would freeze up at the bios splash on startup. Multiple restarts later and a lot of troubleshooting, still couldnt get past the splash. I must have taken EVERYTHING out and put it all back in 3 times. I tried clearing the CMOS, resetting the RAM, everything I could think of, still nothing. At this point, I start to think that I must have fried my processor from the overclocking, so I took out the quad core and replaced it with an old pentium 4 I had lying around, and it worked again. A couple days ago, I decided that I was sick of the P4 framerates and bought another Q9550 to get my pc back to its former glory. After installing the new one however, I get the same exact problem. Frozen at the bios splash AGAIN! Anyone have any ideas on this one?