Category with Sort 0 not shown

This link Das Ende der Symptombekämpfung - Das Gesundheitsforum should lead to a forum-category which has a sort-number 0. Like this, it is not shown in the forum, but I should have to possibility to show the whole category, when I type the above link. But this is not happening and it shows the whole forum (without the above category).

What is the problem?

Thanks a lot!
Marcel

You have turned on an option to replace the forum display page with the forum home + bookmark.

There's a yes/no check box in vbseocp.php admin panel to turn this off

Replace 'Forum Links' with direct links to target URLs?

Thanks, I will try this.
Any negative things out of this (when I had it on till now)?