Even I have the same problem... What I do is as soon as the flight loads I just reset the flight ... It then works fine... I guess it's happening because of not quitting FSX correctly...
Each day FSX creates new new head ache... finally it comes in the form of NGX... its asking me activation code each time I start up FSX... I enter the code it works and all.. when i exit the game it still asks... and sometimes CTD happen... and now its showing I have entered the maximum time and all those crazzy stuffs... really iritated... someone pls help