Copying this post over from mine on HardOCP to see if maybe some Crosshair guru's may think it's a motherboard issue.
Here's the post...
My desktop computer is currently getting "Critical 41 (63)" errors in the Event Viewer. It has to be something with Final Fantasy XI as everything else seems to be fine with it. Ran Prime95 x64 for a few hours on it, no issues. MemTest86+ for about 12 hours, no issue. Can run benchmark tests (FurMark, 3dMark, Batman:AA, Heaven) all day and no issues. Also, I think I distinctly remember seeing this happen before I isntalled the game, but not entirely 100% sure.
Event 41, Kernel-Power
The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly.
When it does this, it loses all my cookies for the Internet as all my auto-login websites I have to re-login again.
So CPU, Memory, Video Cards, [CHECK]... all Ok. Unfortunately, due to the nature of the event, I do not get a BSoD or a dump file created, so it's really hard to pinpoint the exact issue. It can happen with or without Skype running in the background while playing the game.
CPU heat has never been an issue for me as it usually idles around 28~30*C and max load on Prime it gets to about 45*C.
I tried running Skype and FFXI on my laptop and it went just fine for about 6 hours then it happened twice to the laptop about an hour within each other. So now I've been using my desktop for Skype and laptop for FFXI and all his been fine for 2 days (desktop has been running a solid 48 hours straight with 0 problems).
I can't exactly remember if this was happening before or after I installed XI, because I remember browsing Amazeon on IE and the computer, instead of freezing, would just reboot itself with no BSoD, but still ask to choose which OS to boot to within 30 seconds (only running 1 OS, default if shut down improperly) or boot to Safe Mode.
OS: Windows 7 Ultimate x64-SP1
Mobo: Asus Crosshair IV Formula (BIOS Rev. 2002)
CPU: AMD Phenom II x6 1090t (OC'd @ 3.8ghz; even tried to default CPU back to 3.2 and still freezes)
Cooling: Thermaltake Frio (2 fans, push-pull)
Memory: 8GB Kingston HyperX, 1333mhz @ 7-7-7-20-1T
HDD: Kingston HyperX SSD 120GB (latest 3.32 firmware); also tried reloading windows onto a WD 500GB SATA "Green" and it still freezes
DVD: Sony Optiarc 7241S
GFX: Radeon HD 6970x2(CFX); tried 1 card, each card separately; tried both cards; still freezes
PSU: Antec Quattro-1000W
Display: 14.1 TFT LCD
Camera: In bezel
Processor: Dual-Core AMD Turion X2 mobile processor RM-72 2.1 GHz
Chipset: AMD M780V
Memory: 4GB DDR2 SDRAM 800 MHz
Hard drive: 320GB SATA-150 5400 rpm
Optical drive: DVD+/-RW
Graphics: ATI Radeon 3100 shared video memory (UMA)
Ports: 3 x USB, 1 x RJ-45 Ethernet, 1 x VGA, 1 x 3.5 mm line-in, 1 x 3.5 mm line-out, 1 x IEEE-1394 (FireWire)
Battery: 6-cell lithium-ion
As somewhat stated above, it can play on the desktop and laptop for hours then all of a sudden crash, but sometimes it would crash a 2nd time within 15 minutes. Now with the crash outside the game the computer (IIRC; and wasn't running the game at the time? Can't remember for sure) it would reboot the desktop by itself. While in the game, the screen would freeze, keyboard and mouse don't work and speakers go "bzzzzzzzzzzzzzzz".
Things I've tried...
Video Card #1 by itself, still crashes. Video Card #2 by itself, still crashes. AMD Radeon 11.12 drivers, still crashes. AMD Radeon 12.1 drivers, still crashes (used Driver Sweeper both times). Tried unplugging all USB headers from mobo for the front of the computer case as well as a couple case fans, still crashes. Tried unplugging everything USB, still crashes. On High Performance Mode with everything under the sun "Power Save" related disabled. Tried clocking CPU BACK to 3.2ghz from 3.8ghz (OC'd), still crashes.
Things that work: Dragon Age 2, Skyrim, Battlefield 3, PSX/PS2 Emulators. Currently on a 40+ hours Skype call on desktop with 0 issues so far.
Attached is an image. Please Help! Thanks in advance. If there's anything you want me to try or more information required, please let me know.
Event Viewer screenshot