Site categories - wrong links and empty subcategories

I have two problems with Site Categories installed on my test site - http://mowmitato.pl/kategorie/
1. Links are wrong when adding categories into main navigation menu - there's a '/bcat/' part in the url instead of the /kategorie/ url of the main categories page. I've tried many different ways to add/remove/replace/reinstall - nothing works.
2. There's something wrong with subcategories - even though some of them are empty - they are (wrongly) linked, if another one in the same group is not empty. You can see this problem on the page linked above.