Hmm, that's definitely a very strange bug then >.< I'm not sure what on earth would cause something like that cos I don't understand how it would occur in the mac version when it doesn't in windows :( I think to get to the root of it, I'd have to send you a development build version of the game and get you to send me log files so I can have a look through and see if I can figure out what's happening there!
The problem is, I can't actually send a dev build because I've been actively adding to and tweaking the old code >.< I imagine it'd just come up with a whole bunch of other errors since it's a work in progress and a bit of a mess right now :( That's if it even functions at all in its current state.
So I'm sorry about that :( If I hadn't started working on it all again and changing stuff in the last few days, I would've been able to send you a dev build and just try to fix the issue for you by looking at the logs and then quickly exporting a new mac build.
I'm changing the save/load UI in the next update, so with any luck, whatever was causing the issue will be fixed, but if not, I'll have to send you a dev build once the new update is out so I can get to the bottom of it.