The items are adding to the cart for me, i am not able to reproduce the error.
see attached screen shot of items in the cart.
Yes, the localization should not be done to the files in the install directory.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.