Its most probably the light bulb behind the clock. You can test this by swapping light bulbs from another location (I believe there are 5 bulbs back there). You would need to pop out the OBC in order to get to the bubls, to do this feed your hand into the sunglass holder and feel around on top of it with a finger. There should be a hole big enough for your finger to pass through, feed your finger into that hole and you should be able to feel around for the back of the OBC. Now, with that finger, pull on the OBC towads yourself and it should come out. Try to get the top part of it out first, it should be easier that way.
Now that you have the OBC in your hands, look around on top of it and you will see the bulbs. They come in these plastic holders that get screwed into the OBC with a flat head screwdriver and have something like 1.5W written on top of them (sorry I don't have a picture). Be careful with unscrewing the bulbs because sometimes the clips on the plastic holders brake and you have to replace em; although if you think about it, you are probably better off replacing all the bulbs to so that you don't have to go back to do it again a little later.
You can get the bulbs at the dealer for around a buck each as far as I remember. If you don want to diagnose that one bulb better you can swap it around into different locations to see if it works and if the other bulbs work in the clock position.
Hope this helps, keep us posted.