Problem upgrading from 6.1 to 6.2

Hello.

Looking for help with this error message when I tried to upgrade on my local host.
Fatal error: Call to undefined function user_current_to_arg() in G:\www\webapps\drupal\includes\menu.inc on line 594.
Any help would be great. Thanks

* This function translates the path elements in the map using any to_arg
* helper function. These functions take an argument and return an object.
* See http://drupal.org/node/109153 for more information.
*
* @param map
* An array of path arguments (ex: array('node', '5'))
* @param $to_arg_functions
* An array of helper function (ex: array(2 => 'menu_tail_to_arg'))
*/
function _menu_link_map_translate(&$map, $to_arg_functions) {
if ($to_arg_functions) {
$to_arg_functions = unserialize($to_arg_functions);
foreach ($to_arg_functions as $index => $function) {
// Translate place-holders into real values.
$arg = $function(!empty($map[$index]) ? $map[$index] : '', $map, $index);
if (!empty($map[$index]) || isset($arg)) {
$map[$index] = $arg;
}
else {
unset($map[$index]);
}
}
}
}

function menu_tail_to_arg($arg, $map, $index) {
return implode('/', array_slice($map, $index));
}