parent menu items loading its page when clicked

This only appears to happen with a certain combination of DHTML Menu settings. Here's how to replicate:

1) fresh install of Drupal 6.6;
2) turn on DHTML Menu;
3) in DHTML Menu Settings, uncheck every box;
4) now, check "Keep only one menu open at a time." it should be the only one on.
5) save configuration.

Now, when you click a menu item with children, it still dynamically loads the children, but it also loads the page you just clicked on, which makes the whole thing pretty much moot. The default link behavior isn't being intercepted anymore. If you click on an already expanded menu item, though, it does still close the tree without loading a new page. Same for IE7 and FF3.

This bug only happens with "Animated sliding effect" turned off. If you were to turn that on, the module works as expected again.