power supply answers
We run several dozen PC's and other computers in a variety of networks. Our standard policy on erratic power is:
1) Spend 5 minutes pulling and remaking all the main power connections inside the machine, especially the direct-to-motherboard ones
2) If errors repeat, remove power supply forthwith and replace with one of the numerous spares we keep handy for occasions such as this.
Our experiance is that ~10% of power supplies fail in any one service year. Some last "forever", others die the first week.