I got an E5700 up to 12x333=4GHz at 1.4875v. This is well above the 1.45v that's considered "safe" but considering they go for only $5 nowadays...
So I think you really need more cooling. When overclocked and overvolted like this these 65w dual-core 45nm chips can go way over 100w so you need cooling sufficient for quads.
The sad thing is even at 4GHz it's only about as fast as a modern 4.5w tablet processor.