Power supply Playing Dead:
Sometimes a power supply will get "stuck" in a mode, even though it is not overloaded. I don't know what causes this, maybe a glitch/power spike or something, but the power supply will not turn on. "used to work fine before".
Solution: turn off the power switch on the power supply or if it doesn't have one, unplug it from the wall. wait 10 seconds for the caps to drain. turn it back on. if it powers back on your problem is solved. Before doing this I have tried disconnecting all the connectors & reconnecting just the mb to no avail. the solution was the only thing that worked. PC was fine after that. 400W PSU.
Another solution: Tripp Lite 8-outlet ISOBAR surge protector. $57. takes out noise & spikes.
ISOBARs are the best in surge protection.
you should know that the Joules rating is one of the things you look at in a surge suppressor - the higher the better there is an 8-outlet that does 2850 Joules.
other things to know about are clamping voltage, etc, but ISOBAR shines in that respect.
One thing about an ISOBAR compared to other surge protector strips is that it its case is made with metal, so it is not very likely to cause a fire (as many a plastic one have been known to do).
A power conditioner adds an extra level of protection to your system. If I remember right, it protects from brownouts and the like.
3570 Joules. Power Conditioner / Surge Protector, 8 outlets, 8ft cord, (4 outlets spaced for adapters), coax protection
TrippLite ISOBARs, available from newegg.com