Somehow you have your logic messed up. You are using some sort of business logic to relate a shopping cart to a user but, when the user logs out, you are not breaking that link. (Whether it be by a session, a cookie, etc). So, what you need to do is determine how you link a cart to a user and when the user logs out, you need to break that link.
-------------------------
I will only tell you how to do it, not do it for you.
Unless, of course, you want to hire me to do work for you.
^^Thats my signature
|