The onresize_end callback is not a valid function.

This exception occurs when the jQuery UI Layout plugin encounters an exception when trying to execute the code of a callback. It’s not a problem within the jQuery UI Layout plugin.

To fix this, you can comment out the try/catch parts of the callback functionality in jquery.layout.min.js (and then look at the real exception):

  //try {
    // convert function name (string) to function object
    if (isStr( fn )) {
      if (fn.match(/,/)) {
        // function name cannot contain a comma, 
        // so must be a function name AND a parameter to pass
        args = fn.split(",")
        ,	fn = eval(args[0]);
      }
      else // just the name of an external function?
        fn = eval(fn);
    }
    // execute the callback, if exists
    if ($.isFunction( fn )) {
      if (args.length)
        retVal = g(fn)(args[1]); // pass the argument parsed from 'list'
      else if ( hasPane )
        // pass data: pane-name, pane-element, pane-state, pane-options, and layout-name
        retVal = g(fn)( pane, $Ps[pane], s, o, lName );
      else // must be a layout/container callback - pass suitable info
        retVal = g(fn)( Instance, s, o, lName );
    }
  //}
  //catch (ex) {
  //	_log( options.errors.callbackError.replace(/EVENT/, $.trim((pane || "") +" "+ lng)), false );
  //	if ($.type(ex) === 'string' && string.length)
  //		_log('Exception:  '+ ex, false );
  //}