GPU is ATI Radeon X1600 and it's always stuttering and sometimes even causes the system to crash, regardless if it's playing inside a browser window or playing a video stored on the HD. Even iMov is severely limited in audio recording. Is there anything I can do? Logic board was replaced 11 months ago. I'm assuming the GPU is soldered on to the logic board... I suspect this is the source of kernel panics in the past, but I haven't seen any since wiping the system yesterday but the stuttering is still there.