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