Go to Radio Shack and get a can of Contact Cleaner. It won't hurt the plastic , but cover the area under and around the switch, keep the mess in one area, and spray the cleaner in around the switch while you continue to work the switch. Once it releases give it a couple more squirts for good measure.
From the Northwest Corner
Ron's got you covered on this, that's good advise for a common problem on 1500's. I just wanted to chime in with a Welcome from a fellow Keystoner from Schuykill County. We ride up your way a couple times of year. My friends have a Camp outside of Morris.
Just an add-on from what's been said already, after you get the switch cleared up, a couple bursts with some compressed air (also available at Radio Shack in a can) to dry things out and remove any leftover particles that may linger and cause the same glitch.