Need help with problems with trackpad and mouse?

Not sure what is causing this but only started since upgrading my Mac Book Pro to OS Lion but also hot weather here. As computer gets hotter I lose control of both the mouse and trackpad. Have to shut down and let cool down before problem clears. Then wait and restart. Works OK until warms up again then starts all over. Tried having a fan playing over the computer and lifting computer onto a open frame to allow air to get under it but still problems. Any ideas. This didn't happen last year when the weather was even hotter than now.