title: BrowserModule has already been loaded Error
body: <p>I've updated my application to RC6 and now i keep getting this error:</p>
  
  <blockquote>
    <p>zone.js:484 Unhandled Promise rejection: BrowserModule has already
    been loaded. If you need access to common directives such as NgIf and
    NgFor from a lazy loaded module...</p>
  </blockquote>
  
  <p>I'm using lazy loading and my application is broken up in to a lot of lazy loaded modules. However in RC5 everything worked fine.</p>
  
  <p>The only change I've managed to find in the changelog for RC6 is this: </p>
  
  <blockquote>
    <p>compiler: throw descriptive error meesage for invalid NgModule
    providers</p>
  </blockquote>
  
  <p>But since i haven't seen any errors in RC5 this probably doesn't apply here.</p>
  
  <p>I'm kind of out of ideas so any help is greatly appreciated.</p>