Jeff has you on the right track.. Just listen close as you switch positions
A dirty switch usually give a popping or snapping sound when moving.
A broken switch tends to feel lose, or not flipping into position, sort of a catch or drag feeling.
A broken wire (not likely unless circuitry has been worked on) or a bad solder joint that
Here a fist full of wiring diagrams. Take your pick..
http://www.google.com/search?q=ibanez+rg1570+wiring+diagram&hl=en&tbo=u&rlz=1T4ITVB_enUS460US460&tbm=isch&source=univ&sa=X&ei=9SQNUanEHob68gT5y4DQDw&ved=0CDAQsAQ&biw=1366&bih=589
problems could be
dirty contacts
broke switch parts
broke wire
bad pick-up
an Ohm Meter maybe required to prove defective area.
Just my two cent worth..
good luck
