I've had this problem since 2.x something and it still hasn't been resolved. I've tried the solution in this thread to replace the simple apostrophe with a different one, but now I'm getting \\\' instead.
Does anyone else have an explanation/solution to this problem? I've seen other reports of it being attributed to certain plugins, but I'm not using those (buddypress). I don't remember adding any new plugins, it happened after updating WP at some point.