New PC Freezing Issue (Xpervision HD4870 1GB)

Hello All,

Just recently I purchased and assembled a new PC. The specs are as follows

Intel E8400 Core 2 Duo (stock settings and cooling)
Gigabyte EP45T-DS3R Motherboard
4GB G.Skill PC10666 1333MHz DDR3
Xpertvision ATI HD4870 (stock overclocked, revised Palit cooling design)
520W Corsair HX-520 PSU
Antec P180 Case
BenQ 22" 2200HD LCD (1920x1080)
Windows Vista Home Premium 32bit

Before I get to my primary problem, I had a question regard DDR3 timings and voltages. My memory is meant to run with 7-7-7-18 latency timings at 1.65v, however my motherboard BIOS or the windows-based motherboard utility (EasyTune6) only has options to set the voltage to 1.64v or 1.66v. Which one should I choose? Is choosing anything other than what is documented likely to cause instability? What bout the default 9-9-9-24 @ 1.5v?

Now to the main issue I am having. I had some initial teething issues getting the Catalyst 8.10 drivers on properly and that involved some random BSOD's during windows initialisation (IRQ_GREATER_NOT_EQUAL), but once I got that going I wasn't having any issues. I had played some HL2, Warhammer, WoW and UT3 without a problem, and according to the Catalyst Control Center with the fan speed set to 75% the GPU temp hovers around 41-47C, which I understand is reasonable.

Then I installed Crysis: Warhead. First problem I had was jagged, mildly blurry, generally poor quality at native res, but although I believe that was frustratingly unrelated, it led me to fiddle with the settings a bit, and it wasn't long before it was freezing up the entire PC on a regular basis. Concerned, I loaded up FurMark and did a few tests, and by the end of each test I did the PC had frozen up, usually with some sound looping infinitely. During every test and before every crash the GPU never went over 52C, but I don't know how to measure the VRM module temperatures so I cannot report those. After doing some (read: a freaking lot) of reading these modules seem to be my primary concern currently.

I've been an nVidia user for years up until now, so I took a bit of a punt going for the HD4870 (I chose it due to its performance reviews and great value). My worst fear was problems with the card, but I suppose I put most of the instability warnings down to nVidia fanboys. Now I have a genuine concern that my card is overheating or something of that nature and killing my performance. I have great cooling in my case so I am confidant in that regard, but obviously in summer the ambient temps can reach 35 degrees so I want to get to a place where I am not constantly freaking out about my system.

Any advice would be greatly appreciated on both of the issues I have here. Are freezing/overheating issues with this card common? Is it likely that even with the reportedly superior stock cooling of the Xpertvision/Palit card that my VRM modules are burning up and causing the instability? Could it likely be linked to my RAM issue? I look forward to making some progress towards a solution, even if it means getting the card replaced or getting a GTX260 (216SP) instead.

Thanks in Advance!