title: error when doing grails clean or grails run-app after upgrading to ver 2.1 from 1.3.7
body: <p>I just upgraded to grails 2.1.. the latest release available, from grails 1.3.7,
  I have updated the grails_home and path environment variables to reflect this new version. but when I do grails run-app or grails clean I get the following error</p>
  
  <pre><code>Exception in thread "main" java.lang.NoClassDefFoundError: org/codehaus/groovy/grails/cli/support/GrailsStarter
  Caused by: java.lang.ClassNotFoundException: org.codehaus.groovy.grails.cli.support.GrailsStarter
          at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
          at java.security.AccessController.doPrivileged(Native Method)
          at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
          at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
          at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
          at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
  Could not find the main class: org.codehaus.groovy.grails.cli.support.GrailsStarter.  Program will exit.
  </code></pre>
  
  <p>I have groovy ver 1.8.3 setup already.</p>
  
  <p>What am I missing or doing wrong here?
  Thanks</p>