ive had trouble with my immobiliser, do a search theres quite a bit on it, if yours is the same as mine you can buy a bypass plug off ebay (or straight from LR) takes about 10 mins to fit. apparently the "spider" can be a problem with dry joints and you have to dissasemble the dash, take it out and re solder them. Do a search or go through my old posts im sure theres something there that will help you. Have you a second fob you could try? change the battery or take the fob to a garage so they can check there is a signal coming from it, as mentioned above try the EKA code (turning the key in the lock/unlock position to input a 4 digit code that over rides your immobilisor), have you tried simply putting they key in the drivers door and unlocking it manually, I was even asked by the RAC man if i knew of a wireless internet router that could be switched on close to the car that could be interfering/blocking my signal and to go and switch it off (as i was down a council estate at the time there could have been hundreds on), mine just decided to miraculously work 3 hours after the fault started, i put it down to the spider playing up and as such carry the bypass plug in my glovebox just in case it ever happens again. Hope this helps.