Loading scenery etc stuck at 0%

This happens to me sporadically, but sometimes when I'm at the gate and go to the flight planner to load another flight (answering NO to relocate my aircraft, the Loading Scenery, Aircraft, etc. stays at 0%. At this point it seems that the only thing I can do is hit ESC to abort the flight and go back to the main menu.Is there anything I can do to prevent this or force it to finish loading?Thanks.