Q6600 - CPU voltage - How much is to much?

I built a new computer this Christmas and was planning to overclock. So far I've gotten to 3.6ghz and wasn't really planning on going much further. I've been playing a lot of Fallout 3 and Left 4 Dead and the 2 games have been randomly freezing on me. I don't understand why though as I've primed just fine for 10 hours. My current CPU voltage is 1.5550 or so in the bios and stays from what I've seen as 1.512 down to about 1.480 or so. I'm running on liquid cooling and idle I'm at 38 degrees Celsius and under prime around 63 degrees max. Theirs been lots of reports of fallout 3 freezing so I don't believe that is my CPU and Left 4 Dead I'm not to sure of as the picture would simply freeze and the audio would still go and lock up my machine or both audio and video would go and lock up my machine. In the case of Fallout 3 only the game freezes. Is this a problem with overclocking or does the problem lie somewhere else?

I haven't tested on other games long enough to see if it's every game, but usually in Left 4 Dead It happens every few times I play the game (randomly) and for Fallout 3 usually many hours in 4-8. I have latest video drivers for the GTX 260.

More Information:
FSB 1600 V1.5

1.65v

I would tend to stay below 1.5V, though exceeding it by a little won't cause immediate damage.

VID Voltage Range is maximum 1.5 for the Q6600 G0 as specified by Intel's Processor Spec Finder - http://processorfinder.intel.com/d [...] pec=SLACR#

Something seems wrong to me, I've built a bunch of Q6600 computers and all the G0 processors have reached 3.6Ghz at 1.4v - 1.425v just fine using air cooling. If you have load line calibration on your board you should give that a shot and try to lower the vcore. If you are getting a lot of Vdroop that could be why you need such a high vcore to be stable under load.

Without Vdroop my 1.4v drops to 1.35 which is not enough for stable opperation at 3.6Ghz. With load line calibration enabled under load the voltage stays at 1.41v.