JetBrains recently released a new version of IntelliJ IDEA, version 11.1. The new version changed the format of project files in a way that is not backwards compatible with IntelliJ IDEA 11.0 (or older). To use the latest version of CollaboRhythm you will need to upgrade to 11.1 or newer. I am currently using version 11.1.1.
https://github.com/newmediamedicine/CollaboRhythm/commit/8d3881cb764e3200f108f029cb8a15028973b55c