"ASUS P5Q Deluxe discussion".

[PortCitySlim]

I see,
but i've tested my Vcore with SmallFFTs for 3 hours and at the same time i've ran Intel burn test for 5 rounds and was stable. ( with 425 FSB and with only 1.36875 Vcore )
Yesterday while i was playing a game i got application error ( mem. adress error ) than i ran memtest86+ but there was no error.
I tried to run blend test and started to get errors .

You are probably having stability problems with your ram. Set it to as close to 1200mhz as you can get and right at your stock voltage for your ram. Disable Static Read control and leave Read training and Mem OC charger on auto. Set your Performance level to 10 and leave your clock twister on auto. Set your vcore back to 1.36 or 1.37 and CPU PLL 1.56-1.60. Run that and see what happens with GTL's on auto and 1.26nb and 1.32FSBv. Memtest86 will pass even though your blends and ram tests fail in windows. I do not like memtest86+.

Been thinking. If you really want to rule out your NB and FSBv you can set NB to 1.30-1.32 and FSBv to 1.32-1.34. If that fails then your ram is almost for sure causing your problem. I use a 65nm Quad like you and Leeghoofd here taught me most of what I know about this motherboard. Unfortunately for us there are not many people using 65nm Quads and this board so we are kind of left guessing what FSBv and NBv we should be using.