Bloody hell... from what I can make out, those are the 5v lines you've fried... something has gone horribly wrong there.
Personally, test all the components with another rig, but leave the mobo out. That will most certainly have been damaged by the current surge though that. It takes a fair bit to melt the connectors like that, I'm surprised it wasnt on fire.
Either a short, or a fault component could have caused this. Excessive current draw usually only occours when a short is present, or the beginnings of one. If the system was overclocked, then that could certainly have been one cause, but other than that, it could have been anything.