A few days ago I noticed that something was up with the Mac OS X build of Mario SE Beta 9. I know I wrote something about it in another part of the forums, but I thought I'd just type it here as well for easier exposure.
During the transition form the old delimiters to the new ones in Beta 9, something was accidentally enabled that caused the game to read every
file in a map pack's folder, including the infamous "DS_Store" files, which when loaded causes the game to immediately crash and burn on the Stabyourself.net screen. These "DS_Store" files only exist on Mac OS X, and are invisible to users; you can only see them if you pull a folder from an OS X and view it in Windows, where you'll find the DS_Store files intact.
Here's an example of the error in action.