Same thing with Tracon!2012. Took me a long time to get my airports.txt with additional airports to work.
Here s some of my observations:
less than 2 space characters at beginning of each line in airports.txt -> Tracon logs: UNKNOWN AIRPORT: XXX(IATA) ICAO NOT FOUND! Flights to or from that airport do not appear in the sim, SID/STARs not allocated less than 15 space characters between the Country and the first coordinate -> my version of Tracon did crash So I had to make sure each line of airports.txt does start with 2 space characters. Further I did insert at least 20 spaces between the Country and the latitude coordinate. Now it seems to be fixed.
fracasado's post in Tower 2011 having issues reading ICAO codes from airport txt was marked as the answer