I think this might be caused by the autosave plugin but I'm not sure. I disabled it now. You'll have to download the mac build again, but if you do, please let me know if it works now :)
escape to get to the menu and then enter on save/load. If it's not working then you might have to resort to playing it in browser :( I don't have a mac so I cant find out what the issue could be, I'm sorry.
