Fatal error: Class 'osC_CategoryTree'

[lfo]

I have just installed dynamic_sitemap v 2.0 on my local sit web and I have this error message:

 

Fatal error: Class 'osC_CategoryTree' not found in \catalog\dynamic_sitemap.php on line 58

 

This is line : 58

 

  <td width="50%" class="main" valign="top"><?php require DIR_WS_CLASSES . 'category_tree.php'; $osC_CategoryTree = new osC_CategoryTree; echo $osC_CategoryTree->buildTree(); ?></td>

 

 

The file category_tree.php is present in the repertory catalog/includes/classes

 

Which can be the problem?

Where I must seek error?

 

Best Regards