Break the circuit, and install the multimeter (in DC mA current-measurement mode) in series with where you measure the current.
Put the multimeter in the DC VOLTs mode, and read the voltage between the red probe + and black probe -. If the meter reads positive, then the red lead is more positive than where the black lead is connected.
Off hand, I'm guessing that someone hooked up the IR emitter without a current-limiting resistor in series with it, and let out the magic smoke...