Well it sounds like a wire got stretched or pulled out of a tight connection - or maybe a bad ground although bad grounds usually cause other weird things to happen. Try tracing the wire color back to what ever is controlling the lights - the source. I'll bet somewhere along that line you will find your problem. Once you know the wire color, you could just run another one. Also - check the source to see that it is actually activating.
Maybe a wiring diagram would help too.