Keyboard space bar

[CalCajun]

The space bar wasn't working on a Toshiba Satellite 505 and I exchanged keyboards and it's still not working. Plus an external keyboard works. I've also used canned air to clean the receptacle on the mother board that the keyboard ribbon cable attaches to. What could it be?

 

[C12Friedman]

I'm very much thinking an obstruction or deformation on the keyboard tray (or near to) that may be keeping the space bar membrane pinched (the computer would acknowledge and bypass the shorted space bar during POST).
Initially I was thinking the keyboard controller IC but I'd be inclined to believe the problem would then carry over to the external... actually, I'm not so sure about that... could be the controller IC (usually not economically sound to replace/repair if it is the problem).
I say look over the keyboard tray really good for pinched tape or cables or anything not completely flat and check the cable also