Sounds familier. I had this once too. The solution was quite not that funny: my motherboard was broken. Some connections melted down <img src="/ubbthreads/images/graemlins/cry.gif" alt="" />. I hope thats not the case with you. Maybe try this: open your comp and let it cool of for a few hours (maybe night). I had a broken cooling of my cpu once and had to open my case to run the comp (to get enough cooling).
