What I'm about to write now has never happened to me before in all the years that I've been using computers. I would be surprised if anyone here has experienced the same thing happening to their PC and any theories as to what could have happened are much appreciated.
Now onto the story:
As I was about to go to sleep I've turned off my computer and noticed that there was a problem with my wireless weather station (it wasn't showing the temperature). I've reset the weather unit and all of the sudden noticed something rather bizarre. There was a laser like sound coming from my headphones (kind of like that from my those Star Wars movies) and my case which has blue lights started flashing even though the PC was turned off. It would seem that whenever I pressed a button on my weather station the pew pew sound (Yes I know it sounds lame) would go off and the computer lights would flash. I disconnected the headset and tried to turn on the PC. The lights came on and nothing happened. I then turned off the power supply and tried again. Once again, only the lights came on. I then opened the case and made sure that the power supply unit didn't fry as well as that all the cables were secured. I then turned on the PC successfully.
Now the weather station may or may not have had anything to do with it, but it seemed to me as a weird coincidence, especially since I've never seen anything like this before and upon further inspection (when i opened the case) none of the cables were loose and the PC was completely off as well.
Any theories on what could have happened are much appreciated.
I suspect you have an electrical grounding issue. Somehow a power surge caused the LEDs to flare (it doesn't take a lot of power). You having to work with the PSU to get the PC to work would corroborate that guess.