Improved File Browser, Repaint issue

Hi, I am trying to load some files during the Runtime. Therefore, i used the ImprovedFileBrowser from the wiki (http://wiki.unity3d.com/index.php/ImprovedFileBrowser).

It works very fine with the example, but when i try to display the by pressing on a 3D text instead of the GUI-Button from the example, i get an error:

ArgumentException: Getting control 0's position in a group with only 0 controls when doing Repaint

Here the code i am using:

         if (load)
         {
             GUI.skin = skin;
             if (m_fileBrowser != null)
             {
                 m_fileBrowser.OnGUI();
             }
             else
             {
                 m_fileBrowser = new FileBrowser(
                     new Rect(100, 100, 600, 500),
                     "Choose File",
                     FileSelectedCallback
                 );
             }
         }

If i am using the OnGUIMain() function from the example, everything is fine.

thanks for your help