We are getting reports that Studio One 2 is crashing with Mac OS X 10.10 Yosemite.
We found that customers with Native Instruments installed Players or Instruments who also had Avid Pro Tools products installed were having this issue.
We contacted the folks at NI and they referred us to this article which we found to be effective in resolving some issues for Studio One customers who also have Avid products installed.
Please see this article: http://www.native-instruments.com/en/support/knowledge-base/show/3078/
As this situation develops we will update this article.