keyboard help

random letters have stopped working on my keyboard. i have noticed 5 that have suddenly stopped.

i thought maybe somehow some water had gotten under but they are mostly far apart on the keyboard and i dont remember any way that could have happened so i dont think that is the problem.

i have been to keyboard viewer and they are not registering as being pressed.

it is an inbuilt keyboard on mac OS X 10.4.11.

i tried taking one key off and wiping it but that hasnt done anything.

does anyone have any suggestions?
am trying to write assignments and it is really frustrating