Movie maker shutting down

Hello,

my movie maker has recently been shutting itself down every time I edit a movie I am working on. It also does this when I maximise the screen. Before it closes, a notice appears explaining that a problem has caused the program to stop working and that windows will close the program and notify me if a solution is available. It used to work fine so I am wondering if anybody would have any ideas of why it is doing this an what I could do to fix it.
thanks, Bec