This seems kind of odd but I have noticed a couple of my apps have stopped working since upgrading from ios 7 beta 6 to the GM.
In particular, the Any.Do "Cal" app which is one of my essential apps. Basically it closes when trying to perform any option. Someone out there most use this too...I imagine whatever the issue may be it will be fixed next Wednesday or Thursday.
I've yet to experience a problem with the Any.Do Cal app. I've experimented with it and it works like a charm so all I can do is recommend that you delete the app and then re-install it.