Replace the keyboard...
patio.
Before you spend money on a new keyboard, take the one you have into the shower with you. (okay, okay, so you don't have to actually jump into the shower with it, but ensure the water is flowing fast and furious, and hold the keyboard so that the keys face the source of water.) Soak it down good. No soap required. Wash all those nasties away!!!
When finished, shake any excess water out of it and hang to dry. Let it sit overnight even, and reconnect it the next day to see if there's any improvement.
You might be surprised.
RayG