I just installed two new pendant lamps with 12V 20W halogen bulbs in my existing lighting track. One unit works fine but the other unit doesn't. When the non-working unit is connected to the track it made a snapping, crackling, ticking sound and the other light went out. When I disconnected the problem unit the other light came back on. I re-checked all of the wiring and connections and could not find anything amiss. I would appreciate any help or suggestions.

I just installed two new pendant lamps with 12V 20W halogen bulbs in my existing lighting track

The "existing lighting track" is 12 volts isn't it?