renult megan 1.4 hatchback 2004?

I have a renult megane 1.4 and the key card is not being recognised in the car on the dash it says card not detected?? also when trying to start the car if I press the start button the central locking goes crazy and the only way to stopit is to disconnect the battry the immboliser button on the dash board also flases constantly when the central locking starts can anybody help??