I got H4's on my truck, and tonight I noticed my right headlight is out. The strange thing is, however, the high beams are working. Is this a problem with the bulb, or something else? I've never replaced the headlight bulbs in the 10 years I've owned this vehicle, but a couple of months after delivery I installed European Sylvania Silver Stars. They've been there since. Wouldn't be surprised if their time has come...after 9 years!