Probably that aircraft is new in the fleet. The ACARS still has the old registration and ICAO address in its settings and thus cannot perform a sign on - if your company still uses the ACARS then they should get it fixed, if not, set COM 3 from DATA to something else, that should inhibit the ACARS all together (it will complain once with ACARS VOICE and then shut up). If you are curious you can look into the ACARS menu, you should find it has an old aircraft reg programmed.
Last edited by STBYRUD; 15th Sep 2012 at 16:40.