well back again looking for some help... my computer is hard locking randomly. at 1st noticed it when i was playing WoW. at random my monitors would show loss of signal then computer would completely hard lock .i had to hard boot it.. some  days would do it several times others not @ all. I started to run stress tests to check hardware. Prime95 on CPU, Heaven, AvP, 3dmark 11 on video cards, Memtest86 on ram. zero issues passed all tests. also anti malware/spyware etc. tried another PSU i had laying around for a while it hard locked w/ that. gave same PSU to a friend to use and been working great for last several months for him.
 
after messing w/ computer for several months (4-6) i decided to take it to a repair shop to have a fresh set of eyes look at it. they had it for 2.5 weeks. ran several tests i did as well as some others. never a issue for them, even let them play WoW to see what happens. still no issues. they decided to un Prime95 w/ a HPU stress test @ same time didn't lockup. they told me if i wanted the to look further i said go ahead. but i got a call the next business day saying they were too "scared" of my water cooling on computer. so i picked it up....knowing what was going to happen when i got it home..
 
hooked up PC @ home and w/ in 1st 35m hardlocked 3 times. it also did a hard lock w/o any games. just on desktop w/ maybe pandora radio playing while i was serching for answers on web. being i checked alot i started to look @ Bios. making sure mem voltage etc were good. they were but one thing i did notice is my gauge inside my case is reading 4ghz for CPU speed. i have a  2600k which i have never tried to overclock yet, bc when i wanted to is when these issues started. in bios shows the stock speed @ 3.4ghz and my mutipler is correct.
 
i'm about to check myself into a rubber room this is driveing me crazy. i built this rig and worked great for 3+ years no issues. i can normaly fix problems but been working on this for so long i fear it's something stupid that i've overlooked so was wanting some fresh "eyes" to try to help me
 
My Rig:
Mobo: Z68 FTW
CPU: 2600k (water cooled)
Ram: (4) 4gb corsair (1600)
GPU: (3) Evga Geforce Hydro Copper 2 580 (3gb) cards (water cooled)
PSU: Silverstone 1500
Hard Drives: (1) SSD 160gb (OS only), (1) SSD 160gb (Games), (1) HHD 1tb (Games, music, etc)
Watercooling Loop:
Res > Pump > Gpu 1 > Gpu 2 > Gpu 3 > Rad (120 w/ 6 fans Push Pull) > Cpu > Rad (120 w/ 6 fans Push Pull) > Res
 
HW monitor temps: 46-52
 
 
thanks for any help.. i'll supply more info if needed (i'm @ work right now)

yes i tested all them individually then together same w/ my gpu's. i called evga tech support and relayed the issue and they didnt seem to think was a hardware issue.... but i keep think (like i did from day 1) was a mobo issue.... just sucks throwing money into something that may/may not fix issue.

just decided to have some fun... Ran Heaven benchmark & prime95 @ same time..... GPU's Passed never got temp above 38. Prime95 still running.. so far temp hasn't got above 50 (under the HWmonitor tab for 2600k) under Temperature part 68 ........ 
 
this is after my Computer hardlocked 5-6 times on Warcraft...  I have Bios settings set to stock on my z68 ftw. anything i should check in bios or turn on / off

sunday crashed like 5 times in about 40m. so i decided wth and ran Prime95 + Heaven @ same time.. no hard locks..no issues.... next i decided to run 1 of my 3 video cards.. so far no issues..but may not mean much since i can go days with PC working fine...figure test each card alone for several days and seeif i find anyything there... just hate that it's passes all tests i have tried