Long term stability issues with P35-DS3R@E6550 OC

Hi everybody! I've been struggling with this issue for months without remedy! at least I found some pattern to this madness...
first let me start by sharing my specs-


E6550@Zalman CNPS9700
P35-DS3R Rev 1.0 F11 Bios
OCZ Reaper HPC 8500 CL5
Leadtek 8800GTS 320Mb@Thermalright HR-03 PLUS
HX520
HEC case @blow in-220mmside fan-blow out 2x120mm rear/front fans


OC Setup-
fsb -500@+0.2V
cpu multy -7@1.375V BIOS - 1.328V Idle - 1.312V Load
pcie freq - 100/105(tried both)@default V/+0.1V
mch@+0.2V
performance lvl-extreme tRD-8
mem freq - 1000@2.1V BIOS - 2.08-2.096V Real voltage idle/load
mem timings - 5-5-5-15
subtimings - this pic shows what you my BIOS timings&subtimings give me in memset

[IMG]img88.imageshack.us/my.php?image=biosgr0.jpg[/IMG]
[IMG]img215.imageshack.us/my.php?image=30760640ol5.jpg[/IMG]


Now...
When I set my OC something Like this its fully stable 12+ hours in both memtest and dualprime95
but a few days later it starts doing problems - errors in the first min of prime95/memtest , BSODs... Now it has to boot on everything stock or else I can't OC even one 1mhz out of it, if I do boot it on stock I can take it as far as it was with no errors what so ever! its so frustrating because I can't seem to see the reason for it acting up like that! I have another set of ram sticks corsair 6400c4 and it acts up the same way...
tried upping the volts on various stuff but it still happens....
at least now I know what to do when it happens - boot on stock and then back to oc, but before I can do that, I need to know the problem is happening, usualy in the form of data corruption on my disk and that sucks!!!