There is a good chance that your problem may be due to overheating. Open up your PC and give it a good clean. Use tinned, compressed gas and, if necessary, a soft brush. Don't use a vacuum cleaner as you could damage components with the nozzle and the fast airflow can cause a static charge build-up on the nozzle.
As for your ram problem, is it running at the stock speed, or is it running at a higher speed? If it is running at a higher speed, that will result in the altered timings and could also cause a heat issue with the ram modules.