New GPU and PSU, computer crashing

For the new upcoming games this year, i've decided to upgrade my graphics card. The card i got needed a little more power than my current psu could handle so I got a new one of those to.

Heres my card:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

PSU:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

After receiving these and installing them, I was amazed by the performance boost that this card gave me. But now I am getting random computer crashes that require a hard restart to get out of  

Sometimes it happens within 30 minutes of the computer being on, and other times I have run BF3 on ultra for ~6 hours with no crash. Yet funny enough, after exiting the game about 10 minutes later i got the same crash. What happens is the screen just goes black or grey/white bars. The computer still seems to be running, music will still play(sometimes) and i can still talk on skype int he middle of it. But it requires a hard restart to get out of. I've determined it is not a temperature problem at all, but possibly power. I can't isolate the problem, I want to say that its the PSU, send it back and get a diff one, but I will be severely pissed if that does not fix it.

Any ideas on what the issue might be?

P.S. Also im currently running the new PSU with my old graphics card (a geforce 250 gts). All i have to do is wait and see if it will crash to know if it may be the psu or not. =/ halp