Could not load VAADIN/vaadinBootstrap.js in grails

Dear all,
I am evaluating Vaading as framework for our grails applications.
I’m using grails 2.1.0 and installed the Vaading plugin:

grails install-plugin vaadin

Doing this I installed the version “1.7.0-beta10”
The plugin created correctly (i think) all it’s stuff and I found the class grails-app/vaadin/app/MyUI
I renamed it to grails-app/vaadin/p2/MyUI, modified accordingly VaadinConfig.groovy and launched the application (grails run-app).
The application gave me the error:

“Failed to load the bootstrap javascript: ./…/VAADIN/vaadinBootstrap.js”

What did I do wrong?

Thanks in advance!