Can you post your Hub status and logs? Someone should be spot if there is a problem Navigate to http://192.168.0.1 (or http://192.168.100.1 - if in modem mode) Don't log in! Click on 'router status' Copy/paste the data from each of the tabs. The forum software will remove the MAC addresses for you (you may need to click the 'post' button again).
Personally, I always run separate wireless bands and a fixed channel on each. Combined bands and auto channel selection cause more problems than they fix, in my opinion, and that goes for any router with these features and not just the Super Hubs.