Are you using identical ram or different types?
I am using 2 PNY 4 gb sticks and 2 Kingston 4 gb sticks which have different frequencys from each other
You can try this though.
If you have the information available to you from either the packaging or the sticker on the RAM go into your BIOS and change RAM timings to the slowest set (this would be the set that has the highest numbers i.e.: 16-18-18-24 vs 14-14-14-24)
Next adjust your RAM frequency to the slower set (this would be the lowest number i.e.: 2133 vs 2400)
by doing this you might be able to get the RAM to sync properly and then allow you to overclock you CPU without the crash.
If this doesn't work then you need invest into getting identical RAM.