尝试以下操作：http://www.vooshthemes.com/blog/wordpress-tip/wordpress-quick-tip-remove-the-dashboard-update-message/ 这对于2.9版本似乎很有用

//Copied from the above referenced article
remove_action(\'wp_version_check\', \'wp_version_check\');
remove_action(\'admin_init\', \'_maybe_update_core\');
add_filter(\'pre_transient_update_core\', create_function( \'$a\', "return null;"));

add_action(\'admin_menu\',\'foo_hide_update\');
function foo_hide_update() {
    remove_action( \'admin_notices\', \'update_nag\', 3 );
}