Keyboard unresponsive after heavy use.

Hi,

I'm having a problem with my Macbook (ca 2007 model, but updated). After heavy use such as playing modded minecraft for a few hours, the keyboard and scroll wheel stop working. Once the mouse had a fault as well. What happens is that no keyboard commands work untill the fans stop running at high speed. Often one button remains on. For example once the mouse worked, but everything worked as if the shift key was pressed. Another time it was as if the left mouse button was pressed all the time. The problem is system wide. I can leave one app and the same thing happens in finder and any other program I have open at the time. Has anyone got any useful advice? I'm running snow leopard and unfortunately haven't got the installation CDs any longer.