I've now run into this several times. On iOS, occassionally single-finger inputs will just suddenly stop responding. Two-finger map interactions still function perfectly, but suddenly I won't be able to issue commands, select units, or even tap on buttons (not even Pause, Map, or Menu). This seems to happen only when I've made it about 3/4 of the way through a map.
To get things working again, I have to force close the app and restart.
iPad 3 on iOS 8.1.3