GPU Cooling

So I have a single e-GeForce 8600 GTS and I've turned the fan up to 100%, which makes the thing a little loud and keeps it at an even 65°C. If I let the fan auto-handle (via the NVIDIA control panel) it idles around 70°C. I'm not quite sure what the optimum range is for this card, but lately my display has become fairly "snowy" and occasionally the screen will blank to white. I've tried several different monitors and cables but I'm starting to think its a problem with the GPU. I do run my system pretty much constantly, but the system temp is only around 35°C and and the CPU clocks in at 40°C. I'm just wondering if the vid card is getting too hot, or what exactly is happening to make my screen so messed up. Any response would be appreciated. Thanks in advance.