I have had this on occasions and with me it was because I was doing something it didn't like me doing ... in my case it was when doing scene recognition on a film I had aleady edited and exported... the program just kept shutting down every time I tried. When I realised it might be a timecode issue I unchecked the box "apply DV time code as basis for scene recognition" and the problem was cured.

Try to figure out if it closed when you do a particular thing then try to figure out why it doesn't like what you are doing.

Have you tried contacting support via email ?