I'm sorry you aren't able to add a list in Internet Explorer! Sometimes this happens if you haven't closed or restarted IE for a long time, if you have any add-ons/plugins that interact with Constant Contact, or if you haven't cleared out the cache in a while.
Can you give these steps a try to see if it helps?
Please let us know if these work. If you are still having trouble, please feel free to reach out here, or call in to our Support line.