Weighted Categories Issue

I have installed the Weighted Categories plugin and everything works fine except that one category always has a bad link. It seems to only be doing it with the first category with the id of 1. But if I remove all of the posts from that category it will start to do it to another one. I haven’t modified the script at all.

The correct link is like this example.com/tag/categoryname but on the bad link it just puts the category name after the current url.

Does anyone know of this problem? If not is there another plugin that works the same?