New HD 6850 causing system shutdowns?

frankczs

Honorable
Oct 19, 2013
2
0
10,510
This is my first post so please excuse me for the noobness. I just upgraded to a HD 6850 and, after installing it, my system became very unstable. It would suddenly shut down after sometime. It is not even during intense gaming or HD movie watching...just random. After it shuts down, I can power it back up but it'll shut down right away immediately. I would hear some tsk tsk sounds before it shuts down. I think it could be a overheating problem but what's causing it?
If I plug back my 9800 gt it would run normal again though.

Here's my system:

CPU: Core i3 530
Mobo: gateway dx4831 mobo with H57 intel chipset (http://support.gateway.com/s/desktop/2009/gateway/dx/dx4831/DX4831sp2.shtml)
PSU: Corsair cx600
Memory: 6GB DDR3 SDRAM
Storage: WD 1TB 7200rpm
OS: Windows 8 64bit

Any help will be much appreciated!