I had 2 out this spring.
You will find that the bulbs are run in 2 circuits with 2 bulbs in each.. chances are that just one is open.. use an ohm meter to find which one is open and if you are good with a pin point soldering iron you can pick up a bulb from Radio Shack #2760320 White 5mm led. swap it out and it will only cost you $6.00 :2thumbs:
Or $20.00 on E-bay for the whole board......