choppy graphics after idle

hey this is a problem iv been having for about a month or 2 now. when i restart computer everything runs great. but after its been on for awile (mabey 12-24 hours) my games will run really choppy as though im getting low framrates, but fraps shows my rates as normal. i dont show any extra increase in cpu or memory usage either. restarting the computer fixes the problem every time.

specs:
A78NX amd opteron dual core 175
geforce 9800gt
1 gig 400mhz ram =[
corsair tx650w psu

i have current drivers for the chipset and motherboard and i did delete the old drivers befor installing the new.

cpu is 43c at high load 36c at idle gpu is 67c at full load 60c at idle