Problems with all PMDG aircraft

Hello Everyone.......I am having problems with my PMDG aircraft.... I will install it but when I play on the flight sim the game will unload?? Its hard to describe but the Flights, World etc.. menu bar would unload itself after 10 - 15 minutes and if i press ctrl+alt+del the screen will go black and make the windows xp error noise. I have to hold down the power button to get use of the system again!! This happens with the 747 "Queen of The Sky's" and 737NG...... I have no other problems with my FS9... so i think its something to do with the aircraft not liking the flightsim setup but im not sure..... Please I beg you to help me!Thank you all in advanceLegitmodder439