Those temps aren't dangerous, but it's unusual that you lost signal and were forced to reboot. What power supply are you using?
It's a Thermaltake 850W. It's possible it has some problems though, a friend bought it as part of his new build and it refused to boot, so I lent him my CM600 and it started right up. For giggles, I tried his new Thermaltake in my own machine, and had no problems booting, so we called it a swap.