Random Keys Working Sporadically

I have a MacBook Pro OSX, that I bought about 4 years ago. It has worked PERFECTLY for me. Until now. What is happening is at RANDOM times and for RANDOM lengths, a few keys (t,y,u,i,o) will STOP working. It is totally random and there seems to be no pattern to it at all - they simply will work, and the stop, and then work again (as you can see, they are working NOW). I brought it in to the local computer shop (Best Buy) and they did a hardware analysis to see if the keyboard was broken. It came back and said the keyboard was functioning fine. I don't know what to do at this point?? I've read about the battery perhaps swelling up and causing this, but IDK...ANY help would be GREAT!!!!