ORAC has it on the nose.
Lightly soapy water, then water with a little alcohol (not beer), gently use an old toothbrush on it, you want it to look real purty. Let it dry for a while.
WAIT FOR IT!!!
WAIT FOR IT!!!
Then try. The keyboard I am using was given up for dead after a week, after a fortnight, right as rain. The day I bought a new one.
BOFH