Stability problems on a new build

[zaf1981]

I just built a new pc with an ASUS Crosshair V Formula, FX 8120, XFX Radeon HD 6950, 8 Gb Kingston 1866Mhz RAM, OCZ Vertex 3 120 Gb SSD, 1 Gb Western Digital SATA 3 HDD and a Thermaltake 750 Watt PSU.
I have some stability problems with my GPU:
1) Some times when pc posts I have 2 vertical lines on my screen about 3 cm width and when pc tries to boot windows crashes ( a blue screen appears)
2) Some times again when pc posts there are artifacts on the screen and again crashes on the windows boot screen.
3) Some times boots windows normally and crashes after 5-10 minutes or some other times no crash at all (regardless I am playing a game which loads the gpu or using a very light application.
This is not a drivers issue because the problem appears before windows even try to boot.
I used the gpu on other pc with a msi 770 mobo and works perfect (so I think gpu is not bad)
I used an old gpu (nvidia 9500 gt) with the new build and have no problem at all (so i think that the pci-e slots of my mobo is not bad).
All the parts were tried separately and worked perfect.
I wonder if there is any compatibility problem with Crosshair V and 6950 series.
If anyone can help me I will admire it a lot. Thank you.

[HiVizMan]

What I would suggest is put your graphic card in a different PCIe slot and see if the problem is still there.

[zaf1981]

I have already tried it and the result was the same

[HiVizMan]

When you swapped out the 6950 card to the other motherboard did you use the same PSU or a different PSU.

Could you try different power connectors for the graphic card please.

[zaf1981]

The PSU on my 2nd pc (the one with the 770 mobo) is a thermaltake 550 watt. Both PSUs have 2 6pin PCIe connectors. I don't think that a 500 watt psu can support the 8-core cpu and the crosshair mobo. I will try the 750W psu in the oldest pc and tell you the results.

[zaf1981]

I tried for some hours the 750W PSU in my old pc with the 6950 gpu on and everything is ok. So i think that it is not PSU's problem.

[zaf1981]

And something else I forgot to mention earlier, some times my screen splits and it is like i moved it about 1/3 to the right.

[flearider]

if it's a new card it may just be d.o.a .. i'd check another card to see if it still happens .. they may have got to little tim on the gpu ...