(how do I know which version of the software I'm running? is there a version number anywhere)
Well, you're definitely not running the most recent version, or else you'd see the version number on the title screen. 
No fair, you hadn't announced the latest version yet! Anyway do you have any idea what caused my issue? Is that something you fixed in the latest version?
EDIT: hm I just downloaded the game again and no version number is appearing. Maybe you didn't update the Mac download?
Also, the "click to speed up" label on the scrolling text page is gone. hm perhaps some text labels, including the version number and the "click to speed up", aren't working in the Mac version?
Anyway I've played through the Kovit campaign and the issue I hit was "fixed" in the sense that after Dawbry the campaign ends. I hope this is just a temporary removal while you fix issues in the last section, because that battle was cool!
I also noticed there's a new Frozen Heart campaign so I tried that; the game froze after I clicked through the initial dialogue. As in once I was on the screen of the guy saying "It will be as you wish" nothing further happened when I clicked, although I could still move the mouse cursor around.