It locks up. I do not know more than that. Often, it happens right after clicking an action. Sometimes it will do the action before locking up, sometimes it will even update things like inventory before locking up, and other times it won't do anything apparent at all--it just stops responding to anything. I may try to play some more and see if there is any pattern to it (I did finally complete a game and escape the island). I also encountered the bug reported by UnitVector in he comments.