My phone took a trip through the washing machine. Due to this, there was soap underneath the plastic and LCD screen. Take a cotton ball or swab (your pick, but only for this step!) and clean down the plastic and keypad.
If you really want to, just rinse that keypad off in water. There is nothing on it to short out, as its just plastic/rubber. Don't submerge it in rubbing alcohol or else the print may wear off.