I Xed out of MP instead of exiting because it seemed locked up changing flight modes. Frustrated because it was playing with me. Anyway, I got a message saying “ArdupilotMegaPlanner10.exe has stopped working” and Windows would close the program and notify me if a solution is found. “Close program”. Now that message comes up every time I start the program. I even re-booted the computer. Any ideas? My next option is to re-install the program. 
please update to the latest MP version, this should resolve your issue