Big problem using 512x4 dimm w/ Neo 2 (Venice core). At impasse, need advice.

Question

Sorry for the semi-lengthly post but Im at the end of my rope here. Here's my issue.
I have a Venice core and recently added a new pair of 512 x 2 to my system. Same exact set of G. Skill DDR 400 dual channel to go with the original 512 pair Ive had. Running @ 2T w/ default SPD (200mhz 2-3-3-6) I tested Memtest 86+ over 50 passes with all four banks filled, as well as isolating the new pair by themselves for 12 hours which tested flawlessly as well. I also ran all four sticks overclocked (216mhz DDR 433) with 2.5-3-3-7 timings which passed both Memtest and Prime 95 for 10+ hours respectively with no error. Everything seems to be in shape.
Now my problem. I keep getting a nasty lock up every time I run Battlefield 2, the whole system becomes completely frozen and its followed by a nasty buzzing noise in my headphones. The timing of it varies greatly. Most often its been after 5 to 15 minutes of play but most recently its been locking up as soon as the server menu updates for some reason, without even loading up the actual game! I tried different drivers and reinstalled the game to no avail. Im pretty sure its directly related to the 512 x 4 configuration as going back to 512 x 2 the game runs without any trouble.
The very first time the game locked up Event Viewer said I had NFTS corruption as a result of the error. I ran chkdisk and some 3rd party diagnostic tools but nothing turned up faulty. Thinking perhaps it was a voltage issue I upped the memory to 2.75 v, yet the next freeze resulted in a BSoD. It said "Page  Fault in Non Paged Area". Google brings up a ton of different results for that one so Im not sure what to make of it. Event Viewer called it category 102  event 1003.
I flashed the BIOS to 1.9 to make sure that wasn't the issue (it wasn't). Ive tried a lot of different settings in the Cell menu with timings, mhz and voltage. The longest without error (over 30 minutes before it finally froze) was at the default SPD w/ 2.65v. It always fails eventually though. No other game or application has given me a problem with all four sticks running at once. The thing is BF2 is probably the only app I have that actually uses over a  gig of ram at one time though, so its hard for me to be sure its only a BF2 issue at this point.
I could really use some advice here as Im pretty much stuck at this point. If everything checks out in Memtest, would the next suspect be a power supply or motherboard issue? My PSU is a high quality PC Power and Cooling 470w but its gives me some funny sensor readings I have to admit. I never thought anything  of them before since everything was stable until adding the ram but now Im wary. Everest diagnostic tool and the BIOS both report very different voltages, for example Everest says the 3.3 rail is only 3.07 v right now, whereas the BIOS says its at @ 3.15. Everest says the 12v rail is spot on @ 11.98 whereas the BIOS says its at 11.67 (yikes). Both agree the 5v rail is roughly 4.9 give or take. Im not sure if either one is right though, like I said this is the first time Ive had stability issues like this and before the ram Ive had my system overclocked and stable.

Answer 1

Thanks Bejon, Ill run it down 1 by 1.
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- Do you get lockup´s running BF2 at cpu stock speed ? ( not talking about prime or memtest now. Your signature says OC from stock 2,2Ghz to 2,6Ghz which would mean something like 11x237, your post says memtest/prime 11x216 )
Yes, I still experience the BF2 lock up using stock setting for everything (CPU, multi, FSB, ram mhz, ram timing, voltage etc). I must've confused you with the 216 number, sorry about that. I meant to say my OC is 10x260 fsb using a 166 memory divider, which= 216 mhz for the ram (or DDR 433). This passed memtest and Prime 95 as well as stock, but BF2 still locked up with this setting. So basically overclocked or not, using divider or not... I still get the lockup.
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- Did you actually test the 77.76 driver ( not just any differant driver ?)
Yes, tried drivers from the 72 set, 76, and the latest 77.77.
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- Did your experiment with vcore, meaning for example startup 1.425v and cpu voltage +3,3% - still running at stock speed./ Maybe even try 1.6v for AGP.
1.425v +3.3% is exactly what I use for my overclock CPU setting and neither that nor the stock voltage make any difference. For some reason lowering RAM voltage to default (2.65v) seemed to result in going longer without error. I almost made it past 40 minutes thinking I solved the problem with this voltage but it finally caved in again.
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- Did you install any patches ?
Yes BF2 is up to date.
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- Another thing to check is if your Audio / LAN / VGA have some kind of IRQ or driver conflict.
I checked and it turns out I do have an IRQ with two assignments on it. IRQ 21 has both Nvidia Network Bus Enumerator and Standard Dual Channel PCI IDE Controller assigned to it. I have no idea what this means though, perhaps someone can shed light if its a potential root of the problem.
Also whats confusing me is the fact that sometimes when BF2 locks up with 512 x 4 it happens just loading up the server menu, not even loading game data into ram yet!
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I ask these specified questions because I´m running BF2 flawless on another Neo2 system without any hickups with bios 1.8 and a Winchester+Venice stock speed 4 x 512 RAM (3-4-4-8 )and a 6600GT.
Thats kinda surprising to me with a Winchester because from what I understood only Venice/San Diego had the memory controller capable of running 512x4 @ 400+ mhz DDR. Sounds like you got a great chip!
Well thanks for your kind feedback Bejon, sorry if I came off a little snappy before. Im just very frustrated right now. Im going to try and reformat tomorrow just in case its somehow OS/IRQ related. If that doesn't work then Im really stuck. Also if someone can point me in the right direction in how to test my PSU for errors/bad rails Id really appreciate it.