I'm pretty familiar with ALCs, and understand that every access list has an explicit deny any any, so if you just have an "empty" access list it will block all traffic.
I just added two extended access lists to a physical interface, but left them empty. They don't appear to be blocking any traffic??? Are there some cases where explicit deny any any isn't present??? Is there a case where an access-lists on another interface can 'override' this ACL???