Config_Sidebars.php Fatal Error

[buddha 0]

I am close to getting site back up (http://tuxedolandtrust.org); went back to wordpress 2.9, received this error when activating WhiteHousePro3 Dev: Fatal error: Call to undefined function register_nav_menus() in /home/content/b/u/d/buddhatunes/html/tuxedolandtrust.org/wp-content/themes/whitehousepro3_dev/config/config_sidebars.php on line 19