transponderimobiliserkey

hi ,new here tonight,need help with my 1.6s 16v 2001,it started this morn, 2nd /3rd time but put it down to being frosty,drove it 8 mile ,left it til 3.30 and now it wont start,tries for a sec then just cranks!! got a flashing "key in car"light on dash!! is there any known faults with...