Have you still been overclocking your video card?
Id run it at stock, defrag your drive, maybe get a memory freeing utility and see how it goes.
You will see a bit more stability if you get another 256 or even 128 megs of ram.

The times Ive had spontaniuos reboots a few tweeks of the memory and hardrive seem to sort it.

If you are still pushing your 9600pro it is more than likely the cause. Try clocking your ram at your overclock speed and your gpu at standard and vice versa. See who is the weaker link.