title: Eclipse plugin project preference saving exception
body: <p>I am currently developing an eclipse plugin, i created my own property page which will be displayed when right-clicking on the context menu of selected project. I tried to save values of that page by pressing OK button on that page, but i got exception saying: "<strong>Exception occurred while saving project preferences: /test/.settings/com.example.plugin.prefs.Resource is out of sync with the file system: '/test/.settings/com.example.plugin.prefs'</strong>."</p>
  
  <p>Following is what i implemented:</p>
  
  <pre><code>//Get the project
  IAdaptable resource = getElement();
  if (resource != null) {
     IProject project = (IProject) resource.getAdapter(IProject.class);
  }    
  //Define project scope
  IScopeContext projectScope = new ProjectScope(project);
  //Get node by qualified name
  Preferences projectNode = projectScope.getNode(MyPlugin.PLUGIN_ID);
  //set the value and save it
  if (projectNode != null) {
  projectNode.put(PROPERTIES_SERVICENAME, serviceName);
  }       
  try {
  projectNode.flush();  // Exception occurs here!!!
  } catch (BackingStoreException e) {
  e.printStackTrace();
  }
  </code></pre>
  
  <p>To my knowledge, it should automatically save a file like "com.example.plugin.prefs" under runtime-EclipseApplication\test.settings as well, is that correct?
  Anybody has idea how to solve this problem?</p>