This is a quick HACK to fix the boolean modifier freeze. IT IS NOT A BUG FIX!!! I tracked a freeze-up down to this module (see the link below for details). The max iteraction value I picked is completely arbitrary, but in my mind seems like much more than one should need.

https://projects.blender.org/tracker/index.php?func=detail&aid=3295&group_id=9&atid=125