'Mark as Unread' button doesn't work with unread posts

[Aatrek]

If there are any unread posts remaining in a thread, where the blue "arrow" button appears on the main thread listing page, the red "X" mark-as-unread threadlisting button only acts as a link to Page 1 of that thread.

If no unread posts remain in the thread (red "X" appears alone), the button works fine.

Running on Chrome Version 23.0.1271.97 m