CTD using GPS

Hello I sometimes, not always, have a CTD with automatic restart when I use the default GPS and try to enter the ICAO code of an airport using the "direct to" function.It happens on different aircraft and on different place of the world, with or without specific scenery.I run FSX SP2 on a core2duo E8500 with 4 giga Ram and a Nvidia 8500GTS video card - Vista 32.Main adds on : REX, PMDG JS41, Real Air Duke, Aerosoft Twin Otter.Any idea would be welcome.