Problematic graphics card or both motherboard crossfire slots faulty?

[portasgr]

A month ago I built my budget-gaming PC, but from day one I get all the time random BSOD, crasses, errors and programms to stop working! I discovered the reason why I get all the problems is related with my graphics card, because when I disconnected the card and let Intel's i5 integrated graphics do the job the PC behaved perfectly! My motherboard has crossfire slots and with my graphics card connected to either of them my PC will behave the same problematic way! So my question is how to tell if the problem comes from my graphics card or the motherboard slots?

Graphics card: Sapphire Radeon HD7770 1GB
Motherboard: Asus P8H77-M

 

[rgd1101]

psu?

 

[portasgr]

psu?

Corsair Builder Series 600W V2, but I think it works fine, at first I bought a faulty one, but I gave it back and got a brand new... I think the only way to determine what's wrong is to borrow another graphics card and test... Any ideas anyone?