Problem with my Radeon 260x

Hi there,

I just recently purchased a Asus 260x DCUII OC to replace my gtx280 which kept overheating.

I know it's a PCI-e 3.0 card in a PCI-e 2.1 slot but it should still work
And not give me any grief. I thought I could get this until I can upgrade my mobo and processor.

It keeps freezing/black screening me like my monitor has turned off
Yet it hasn't. It seems to freeze on restart or opening the catalyst centre
Or installing programs. I installed this on a new hard drive with fresh windows 7.

My system is

Gigabyte x58 extreme 1366 socket
Intel i7 D0 920 2.66ghz watercooled.
12gb corsair 1600 ram
Corsair hx1000 watt psu

Any ideas as to why this new graphics card keeps crapping out on me?

 

check bios & disable cpu speedstep other than i can't help