Thanks for the reply.
FYI, I am an avast5 free user. Also, I don't perticularly like avast's way of handling sandboxing, which is one of the reasons why I don't have the paid AV, and I prefer sandboxie. However, I think providing a sandboxing feature is a step in the right direction, and alwil has made many steps in the right direction lately.
Also, about the permanent browser cache, sandboxie can be configured to allow your browser to have direct access to the normal cookies, history, and bookmarks, and presumably cache databases.