Problem with my HIS 4850 ICEQ4 512?

Hi, I just built the system a few days ago

OCZ 500W PSU
e7400
HIS 4850
GSKILL Ram 2x2gb
Gigabyte EP43UD3L

After playing Age of Conan for an hour or two, I begin to notice that my FPS starts to get lower as time goes by. I usually average around 40-80 fps depending on the area. And 40 fps in towns. But after a period of playtime, I suddenly am stuck at around 20fps no matter where I go or what is on the screen. At this point, I restart the computer and everything is fine.

I am running CPUID hardware monitor and Fraps in the background.

For my temperatures, I am reading

32 C Idle and around 39 C load for the CPU

The graphics card idles at around 56C with ~25% fan speed, and during my gaming I usually notch it up to around 50-60%, so that with load it is still relatively cool at around 56C. I was just wondering if anyone had any idea what could be wrong? I'm gonna play a few other games for an extended period of time and see if the same type of result occurs.

Edit: I'm playing at 1440x900, and I have left the gpu and cpu at stock.

Thanks in advance.

i think hes using a 2 duo e7400!