Nothing turns on at all? I would double check any of the power connections to the cpu and mainboard power, the various wires that attach to the board from the front panel including the power switch. Make sure none of them got bumped loose. Make sure nothing is touching like a screw or anything stuck behind the motherboard potentially shorting anything. No wires pulled extremely tight that may be putting stress on any of the connections to the plugs. Nothing pinched like a wire between components.
Something you might try, a basic power on test for your power supply. Scroll down to where it says 'paperclip test'.
http://www.corsair.com/en-us/support/faqs/power-supplies
It doesn't completely clear your psu but it will at least give a basic idea if the power supply is turning on or not. If it does turn on and if you reconnect everything in your case and it still won't power up there's a chance it could be the power switch on the case being faulty.