Installing Second Graphics Card Causses Reboot Loop

[Daaze]

I recently just bought 2 new graphics cards for my computer, as well as a new psu since my last one died when I put in the graphics cards. For some reason, with both graphics cards in, my computer will constantly reboot itself. It'll get to the point where I select to boot windows, and when I do, the computer restarts. However, after taking one card out, it starts up fine. Any idea what might be causing the issue?

Computer Specs:
2x EVGA nVidia gtx 960 http://www.newegg.com/Product/Product.aspx?Item=N82E16814487091
6x Kingston HyperX 4GB DDR3 1600 RAM http://www.newegg.com/Product/Product.aspx?Item=N82E16820104339
EVGA LGA 1366 Intel X58 ATX SLI LE Motherboard http://www.newegg.com/Product/Product.aspx?Item=N82E16813188049
Intel i7 Bloomfield quad core 2.66ghz http://www.newegg.com/Product/Product.aspx?Item=N82E16819115202
Western Digital 1TB 5400rpm 64mb cache 3.0 GB/s SATA http://www.newegg.com/Product/Product.aspx?Item=N82E16822136490
ASUS CD/DVD burner/drive http://www.newegg.com/Product/Product.aspx?Item=N82E16827135204
EVGA SuperNOVA 1000W PSU http://www.newegg.com/Product/Product.aspx?Item=N82E16817438010

Wanted to make sure to include everything since I have no idea what would be causing the conflict with a second gfx card.

Although, I haven't tested the second gpu in place of the first one to see if it might have been that graphics card that is being faulty, but I wanted to post this to see if there might be any other suggestions before I get back in and mess around with the computer so I can kill two birds with one stone.

 

[Daaze]

I think I may have figured it out, the graphic card was in an x4 instead of an x8 slot. I haven't been home to test it in the x8 slot, but would that cause a Reboot loop?

Edit: This wasn't the issue. I tried the both graphics cards in both the x8 and x16 slots. Whenever there was only one of them in, either card in either x8 or x16 slot, it booted up normally. Whenever the second card was input (one in x16, one in x8) it started a reboot loop.

 

[Daaze]

I know we're not supposed to bump topics, but does anyone have any ideas? I'm honestly at a loss here. All drivers are installed, each card works fine individually in either slot, each card gets read fine, gets power... I'm just completely stumped on this, and was hoping to avoid returning one of the cards.