BSOD with 4 x 2Gb Kingston DDR2 800 Mhz KVR800D2N6/2G in mobo P5Q SE

Hi all and thanks for reading
I have random BSODs since I upgraded from 4Gb to 8Gb.

Before I had 2 sticks x 2 Gb KVR800D2N6/2G and had no problem.
Since I bougth 2 addional and IDENTICAL sticks I have random BSODs (once a week approx).

All sticks have been individually tested one by one with no error in 2 different Pcs. with Prime95 and memtest 4.0.

My question is:
Is there some kind of incompatibiliy with 4 sticks of 2Gb Kingston DDR2 800 Mhz KVR800D2N6/2G in mobo P5Q SE?
I have read someone saying that they cause crashes when they are all set together in P5Q SE.
Is this true?

Thank you and best regards

p.s.
My system:
Win7 64bit SP1
P5Q SE (bios 1005)
XFX ATI HD 6870 1Gb DDR5, drivers 12.3
8 Gb (4 sticks x 2Gb Kingston DDR2 800 Mhz KVR800D2N6/2G)
PSU 700W Tacens