Category structure Changes at random

I’m using wordpress 1.5 with the stucco theme. I am getting some strange behaviour in the category structure. On the main page the structure looks fine. Links are all where they should be. But when clicking on the category links the category structure changes. Categories become subcategories of other categories which they should not be. Also when this happens clicking on these category links that have moved brings you to the wrong category.

I’ve tried deleting these categories and then putting them back but the problem persists.

The site is at
http://www.ourvalleysprings.com/vsblog/

if you’d like to see. I really appreciate any help. This is wierd and frustrating.

I have searched the forum for this problem but haven’t found it.

Thank you very much

Phil