We have a track light that has been up for a year with no problems. One bulb burned out (we thought). We got a replacement bulb from the hardware store and changed it, but the bulb still won't work. We checked and the bulb is the correct type. It plugs in fine, fits snug, and everything seems fine... except, no light. What else can be wrong with a track light? We are inexperienced with this type of fixture. Thanks.