screen resolution problem

I am trying to run FSX on my new computer core i7 64bit nvidia GTS 450, the only problem that a see at the moment is that when I start a new flight with PMDG 747 or LDS 767 the sim is runing fine but I con not use the mouse on the 2D panel,only if I change screen resolution the problems are gone, maybe 1 hour or to hours later in the flight I get the same problem, no nobs response with the mouse cursor, if I change the screen resolution on midflight then the problem is gone, the only thing that I did was to use the nvidia inspector to set it up for FSX as per the guide, but the problem remains the same.Please help me!!Best RegardsRicardo