beakybird ... fortunately, I've never experienced the problem so unfortunately, I can't help ...
124's suggestion sounds like a good one ... have you tried this:
http://www.amazon.com/CRC-Electrical-Contact-Cleaner-Aerosol/dp/B003NTQCA2
customer reviews look good ...

BTW ...sorry to have continued this thread down the wrong path ... don't want it to get to the point that you have to 'weed' out the helpful suggestions ...