[Plugin: Custom Post Type UI] Get Error after install the plugin

Hallo,

I have install the Plugin: Custom Post Type UI on my site and all working good i have great Post Types and Taxonomies now i want to show the Post Type in my menu wenn i go to Appearance -> Menu it show a error

Catchable fatal error: Object of class WP_Error could not be converted to string in /home/******/public_html/******/***/wp-admin/includes/nav-menu.php on line 73

Can some on help me by this or tell me what i have do wrong all taxonomies name have small letters.

will be very nice if some on can help me.

http://wordpress.org/extend/plugins/custom-post-type-ui/