Corsair dominator 1066 in Gigabyte P43 motherboard

It's the RAM. Using overclocked RAM often is challenging. Did you set the voltage and timings correctly? If they are unstable at 1066 MHz, then run them at 800 MHz and tighter timings.

Try it at 2.15, or 2.2
On an Intel system unless you doing some very heavy overclocking, you don't need 1066 memory. The memory controller is tied to the FSB, so running memory faster than 400mhz, (800mhz ddr2) is really pointless. (Does not pertain to socket 1156/1366, the memory controller is on the CPU, like AMD, changes everything about how the memory works)
Your CPU is using a FSB of 333mhz. So plugging in memory that is faster has little benefit.
You would be better off by getting 800mhz ddr2 with a good combination of the tightest timings, and lowest voltage you can find.