title: "Sources directory is already netbeans project" error when opening a project from existing sources
body: <p>I've installed NetBeans 6.9.1 and installed few updates for it.</p>
  
  <p>Then I've created a new project from existing sources. After a few changes I've closed it. And now I am having an error, when trying to open a new project from existing sources (the same files):</p>
  
  <blockquote>
    <p>Sources directory is already netbeans project (maybe only in memory).</p>
  </blockquote>
  
  <p>After Googling it, I noticed it happened not only with me. But I didn't find the correct solution. I've tried to restart the IDE, I've tried to restart the PC, I've tried to reinstall NetBeans. Nothing helped.</p>