I would also guess that gunk has gotten into the keyboard. These traces are not exactly gunk proof.
If you look at how most dome style keyboards work.http://en.wikipedia.org/wiki/Keyboard_technology
If you are good at opening things, you may be able to fix it. laptop keyboards are insanely thin so take your time.
If you are not into that, see if you can get a new one from Acer, even at a cost it is cheaper then replacing a computer.