I only tested it with my Nexys Board, I don´t even have a emulator, so I´m not sure, how it behaves on other platforms.
I have tested it with xmega65 emulator. It works fine!
It's a nice piece of software. One small point I would mention: To re-calculate the cells I would find it better, if a single keypress would do it. At the moment you have to press F5 and then 4, or do I oversee an option?
I like your program! Great work!