I am having a similar issue - the symptoms of mine are as follows
In Internet Explorer 7 ONLY
- Add a product to the cart on the category page results in a redirect to the home page
This functionality works fine in Firefox, Google Chrome and Opera. I can reproduce the problem in IE on multiple computers (all IE7). I’ve been through some of the troubleshooting steps in other threads and no joy. Some info on debugging this would be much appreciated.