There is an incompatibility between Adhearsion 1.0 and Rails 3.X, namely Adhearsion uses rubigen to generate the Adhearsion directory structure for both the ahn app and any component, rubigen 1.5.5 is the latest version but it requires
activesupport ~> 2.3.5. Even if you have a perfectly good activesupport 3.X installed rubigen will not use it, and ahn create will fail.
Now watch in awe whileahn creates your app skeleton! bklang, our project maintainer has made a pull request to the rubigen maintainer Dr Nic, so hopefully sooner or later a newer version of rubigen will make this unnecessary.