Index: wp-admin/includes/screen.php
===================================================================
--- wp-admin/includes/screen.php	(revision 19052)
+++ wp-admin/includes/screen.php	(working copy)
@@ -466,7 +466,13 @@
 					break;
 			}
  		}
- 
+
+		// The post_type must be registed for the taxonomy.
+		if ( $taxonomy && $post_type ) {
+			if ( ! in_array( $taxonomy , get_object_taxonomies( $post_type ) ) )
+				$post_type = '';
+		}
+
 		switch ( $base ) {
 			case 'post' :
 				if ( ! $post_type )