Andreas, this "doc fix" commit appears to have broken the code.

On Fri, Oct 29, 2010 at 04:43, <ecker@users.sourceforge.net> wrote:
Revision: 23634
         http://qooxdoo.svn.sourceforge.net/qooxdoo/?rev=23634&view=rev
Author:   ecker
Date:     2010-10-29 08:43:48 +0000 (Fri, 29 Oct 2010)

... 
Modified: trunk/qooxdoo/framework/source/class/qx/ui/table/model/Simple.js
... 
===================================================================
-     * @param ascending {Boolean}
-     *   <i>true</i> for an ascending sort;
-     *   <i> false</i> for a descending sort.
+     * @param columnIndex {Integer} index of the column
     */
-    _setSortColumnIndex : function(index)
+    _setSortColumnIndex : function(columnIndex)
    {
      this.__sortColumnIndex = index;
    },

You changed the parameter name but didn't change its usage in the function. That should now be

  this.__sortColumnIndex = columnIndex;

Derrell