FS9 in windowed mode problems

Hey guys I got my computer conected to my tv via HDMI cable, the video card is a 8800GTS 320 mbs.
The thing is that when I fly in windowed mode and click on another window (ie firefox) and then click back on fs9 the fs9 screen goes black, I can hear the plane, if I launch my gps I can see that the plane is still going. But I can't get the image back.
I can also click alt and use the menus at the top, but my fs9 window remains black
any ideas?
thanks
Dan
The thing is that when I fly in windowed mode and click on another window (ie firefox) and then click back on fs9 the fs9 screen goes black, I can hear the plane, if I launch my gps I can see that the plane is still going. But I can't get the image back.
I can also click alt and use the menus at the top, but my fs9 window remains black
any ideas?
thanks
Dan