So uh... My PC won't turn on. I shut it down then switched out a monitor and now it won't come on. I see the leds on the mobo are lit though... So it's getting something. Did my on/off button on my case go out or something....?
wth
The only time I've experienced something like this was because of a power delivery problem of some sort; a spike or surge perhaps. Try unplugging the PSU from the wall socket and leave it for 15 mins.
If you still have no joy, you could try triggering power on without the switch by bridging the pins on the motherboard with something conductive. Fingers crossed it's nothing serious.