A couple of times I have meant to create a fleet from stacked ships, and hit the "F" command without first selecting more than one ship. Of course, a message comes up saying that you must select more than one ship to create a fleet, but clicking on that message results in the same error message coming up over and over with no way to get rid of it except quitting the game. My fault for not selecting the ships for the fleet, of course, but the game should not freeze.
