I was recently installing the updated application from scratch on 10.10. I had previously opened and older version of the game on an older OS version 10.8.5 even though it didn't officially support it),

Anyway I wasn't making it to the menu screen it would just launch to black with a spinning beach ball. I threw away the MBWarband folder in "users\(your user name)\library\application support" as a test and it worked so if this happens to you try it. Note that in new OS versions the library folder is hidden.