It is well known that many MOBOs have a hard time running four sticks. Ways to fix this are to run at slower bus speed (just the RAM, not the CPU), relax the timings (if 4,4,4,12 try 5,5,5,15) and bump the voltage. Alsio sometimes a bump in the Northbridge violtage.(not necessarily all of those things but one or some combination
The fact that you pass memtest and Prime 95 is good but that does not necessarily mean you are stable in windows. Maybe, maybe not. But I would explore the RAM settings because I cannot think of any better thing to try. The clue here is that the system is stable with 3 sticks but not four, this argues against a software problem. Anything is possible of course.
Also at least try the hotfix I linked. If it does not apply to your system it will refuse to install