Welcome to grails-vaadin plugin. 

Official plugin has not been maintained for 10 months and many people need to use new version of Vaadin and maybe also new version of Grails. I have took this plugin: http://grails.org/plugin/vaadin and upgraded version of Vaadin to 6.7.4 and Grails 2.0.0. 

Info about plugin and installation: https://github.com/ondrej-kvasnovsky/grails-vaadin-plugin/wiki