if the bulbs are imitation HID bulbs then that would explain it. For some reason (probably because most companies are capitalists) those imitation HID bulbs like to go out every 30-45 days. if the packaging states "HID" somewhere on the label but the bulb plugs in directly to the car's harness (like the stock bulbs do) then they most definitely aren't HID's, and like 98gsrDC2 said; real HID bulbs need a ballast to work.