immobiliser trouble?

Hi there,i have a Subaru forester which ive been using for work which has been great in the bad weather until last week,i left the car for a short period of time and when retuned the key fob stopped working and also stopped the car from starting.All of the ingition lights still work and the car battery is ok ive changed the batteries in the key fob and still no joy.The AA came out to me and messed about for an hour but didnt seem to have a clue..The alarm is a Thatcham(M.I.R.R.C.)Cat 1/immobiliser M30/tc2-808/0189 any help getting me back too work would be appreciated cheers