Just thought i'd throw in my 2 cents.

Does your car have the flip out key type with the 3 buttons for locking/boot/unlocking, and if so, is this still working well from a bit of distance away from the car, ie it's still locking/unlocking doors and lights flashing etc. If this doesn't work well (or at all) could it be just the battery in the key thats dead and now it won't turn off the immobiliser.