When I install your post I get when I change the category to on or off the message "Warning: Cannot modify header information - headers already sent by (output started at /home/mbs/public_html/shop/admin/categories.php:979) in /home/mbs/public_html/shop/admin/includes/functions/general.php on line 22".
I have been using the QPU for a long time. Just set up new store on new server and now only the Category drop down is working. If I select a manufacture from the drop-down it shows the correct selection in the address bar (Ex. quick_updates.php?row_by_page=20&cPath=&manufacturer=19) but it is like it never executes the command and I get all products listed again. Same thing happens for "Lines Per Page". Any sugestions? BIG THNX!!