faulty 98 renault megane immobiliser?

the immobiliser warning light is flashing on my 98 megane yet the car runs fine, i would like to avoid a trip to the dealers as they want and arm and a leg for taking a look and 9 times out of ten it comes out worse than it went in, could anybody shed some light on this problem before i pull the bulb out as seeing it flash just make me feel im not going to get where im going...