I have had problems with my juno2 and w30 where odd keys stop working and it was dust under the rubber contacts .oh yeah and a punter spilt his bourbon dowm my A50 and took out about 16 notes ,which came right after a clean (bit annoying when you're out of town though damn it).Unless you've had a spillage i cant really see dust or dirt being your problem,still it wont hurt to give it a clean
you never know