Computer freezing randomly due to browser usage


Nov 7, 2010
Hello, I have just build a new pc, and everything seems fine. Even overclocked from 3.3 to 4.5. Ran Prime 95 for 12 hours and totally stable. But for some strange reason when I use the web browser such as Firefox and Chrome my computer just freezes randomly. It could freeze in 1 minute or it can freeze in 10 hours. It's really bugging me. I'm not sure if its driver problem or hardware problems. (Kind of a newbie here).
If its hardware problem please tell me which part so I can RMA it as soon as possible.
Here are my computer spects. Please help me out, Thx =).

CPU: i5 2500k sandy bridge
Mobo: ASrock p67 extreme 4
Ram: g skill ripjaws x 8gb 1600mhz
GPU: msi twin frozr gtx 560ti
HDD: samsung spin point f3 1tb 6/gb/s
PSU: 700w ocz modxstream