I just experienced the same issue. Copied the .ccf to my IPAQ, learned some functions, copied it back to my PC, and ProntoEdit started to open it then closed in the blink of an eye. Luckily I had saved a backup of my .ccf so did not lose any work. From now on I will backup every time I copy to my PDA. Anyone know a possible cause for this issue? My .ccf is not terribly large (406 kb), so I am guessing that there is some learned command that is incompatible with ProntoEdit?