That happens on windows sometimes too, when you accidentally try pasting nothing. I'll forget I emptied the clipboard by copying something on windows or something that no longer exists then I'll paste it into somewhere thinking I've still got an action in the clipboard, then lights out!
Anyway... for mac users: I would recommend using the windows version of the editor on a windows machine if possible or in a VM (if you don't have a windows machine) - well at least until the mac os editor is a lot more stable. In comparison to the windows editor, it still has a long way to go to become as stable / working from what I've seen when I had a go with mac editor.
Hopefully it will be a lot more stable once the devs manage to rip out & replace WxWidgets - bane of most editor related bugs on both windows & osx!