FS-2004

I have a question for the forum. I have been having trouble with some of my planes while in flight. All my gauges will suddenly go out. To retrieve the gauges while in flight I have to save the flight at that point and then restart the flight and all my gauges will come back on. needless to say this is a hassle and this can happen more than several times depending on the length of the flight. But, this problem doesn't effect all my planes. My question is, does anyone know what is causing this situation. any help will be greatly appreciated...