Humm...okay, well the following line is still in the default config file for 1.8. In previous versions you just uncommented it to get the same behavior. You may try adding the following line to your config.php file and see if that helps....also, make sure it's not already there and set to false...that could be why it's not sticking.
$CFG->allowvisiblecoursesinhiddencategories = true;
Steve