I am using Zen Cart 1.3.8a

My Manufacturer / Category Filter works fine on the manufacturers_all_product page.

What I am trying to do:
I would like to insert that filter (drop down select form) into another page.

What is Happening:
I have managed to do so but when a category is selected (clicked-on) it directs me to the shopping cart page.

Any suggestions to why this is happening?
Anyone know of a simple way to call the feature on a different page other than the manufacturers_all_product page?

Any help would be great!
Thanks