The problem is simply due to a dud bulb behind the display. If you look at the clock closely I reckon the display is still there - you just can't see it! To get at the thing, the entire dashboard top comes off. If I remember correctly you prise off the speaker covers at the corner to reveal screws underneath - the dash top then lifts upwards to reveal the back of the display and the bulbs come out with their holders. Renault will rob you for the bulb - you could try a motor factor but they aint so common. Hope this helps!
John
February 2008