I had the same thing happen in Beta testing and had to keep 2014 available for live performances. Once 2015 Build 102 was available the problem was solved.
When it did freeze was at the very beginning of the start up when the BIAB logo was on the screen, before the main window opened up.
There was a very long report that also came up.
The program works well now on 10.7.5 and a recent upgrade to 10.10.4