[Plugin: jQuery Portfolio] Warning: call_user_func_array()

I get this warning when I add/edit a portfolio item:
Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, ‘Portfolio::metabox_register’ was given in /../wp-includes/plugin.php on line 403

http://wordpress.org/extend/plugins/jquery-portfolio/