FSX CTD when loading some missions

Hello,I recently purchased FSX and have installed it along with both SP1 and SP2. I have not installed anything else. I can go into free flight mode all I want with no issues but some of the missions crash to the desktop after it gets to 100% loaded. Some missions do actually get into the sim and they seem to work fine until I get the hit escape at the end. When I hit escape all sounds stop and the screen freezes and a CTD window shows up under the simulator window. Another escape and the sim restarts. I was just wondering if anyone knew how to fix the CTD with missions. I can only get the awards that occur durring missions and not the ones awarded for finishing because of this problem. The only other CTD I've noticed is trying to access the display properties while in the sim. Thanks!