I recently had a problem with wordpress 3.6 and the function wp_list_pages within my template. I know my page had subpages, but when I executed the code the function returned NULL. After doing some digging I found that when wp_list_pages runs, it applys a ”exlcude”-filter, and somewhere on the way this filter added all my pages to it. I tried deactivating all plugins, search all code for the exclude filter funtion and tried another theme but it did not work.
So for now I just added comment marks infront of line 842 in fil ”wp-includes/post-template.php” which temporarly solved the problem.
I know this is the forbidden way so solve it =) so if someone has a better solution, please put it in the comment section.