If the LED battery light is on and the c/l locking part of the key is working, it may just be your actual car battery. If the volts are down for any reson it can wreak havok on the key thingamy. Try jump leads to the battery terminal and allow car to power up, then see if the immobiliser deactivates. (This happens with Meganes, the older ones so I'm sure your Laguna is the same)
Lou, August 2007