;) i've experienced similar bug. FSP suddenly poped up a FSX map, and said - you cant slew. Ok, i said, but after i closed window - FSP said that i tried to move Aircraft and terminated flight.

You case looks the same, but with another menu. And if fuel and payload menu used, its quite possible that it sets SPEED=0. Thats the possible reason why you got a stall after quiting menu.

Actually its not FSP problem, that module (uiautomation) - a part of MS NET Framework. it used by developers and FSX itself to get acess to menus. and its buggy offcourse >:(
CIVA INS or any addons only increase possibility of some bugs happening. Since they all using that MS NET Framework.

Try it, and if it not helps, we'll find something else :)
Have a nice fixing  ;)