Error message in Admin Interface

Since upgrading to the latest version of the plugin (both using the WP interface and after getting the error, manually via FTP) I get the following error on all admin pages:

Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, ‘GA_Admin::add_config_page’ was given in [server root]/wp-includes/plugin.php on line 339

Previously the plugin was fine and the plugin is still working correctly on all the other pages on the site appears fine.