Remove the program, then remove file ~/.midgard2/data/maecalories.db and then reinstall.

or remove file ~/.midgard2/data/maecalories.db and start the application and wait patiently while it initializes the database from scratch (this can take over 5 minutes easily).

Edit: To "remove file" do the following:

1. open terminal
2. type (or copy paste) the following command
"rm ~/.midgard2/data/maecalories.db" and press enter.

I already thought about adding a relaunch counter to the app and if we run into this same bug twice in a row then it would do something smart about it.