Can't add new category after security patch

I added the security patch (security_patch_v138_20090619) according to the instructions. I did a manual update of the "html_output.php". I do not get any error messages after adding the patch. I am able to add new products, but not categories. When I click "save" a new category I am redirected to my-admin-folder/index.php

I have only two additions installed:
Dynamic Price Updater
Fast and Easy Checkout

Zen Cart v1.3.8a/v1.3.8

I would appreciate any help in fixing the problem :smile:

Solved!

I discovered I had mixed up the folders where i uploaded the html_output.php. I got confused by the structure with folders and files having the same names both for the backend and frontend sections. Sorry for this post.