Fix Iphone Navigation Back Buttons & other small issues

I have an iPhone project which I have added Three20 to for the launcher. 1. The user logs in 2. Chooses an aquarium 3. The launcher is shown there are some bugs and I think it is centred around the root view controller basically the following problems exist and need resolving as part of this project 1. when you go to change aquarium from step 3 back to 2 the left nav back button does not appear 2. when you log out the application seems to hang 3. when you enter an incorrect username and password the application hangs 4. I have made a "home" button to go back to the launcher page, but would actually like the navigation history to work properly 5. A strange thing happens when you change aquariums using the selector view, it works fine in the simulator in IOS4&5 but in IOS5 the launcher appears on top of the sub view being opened. I think the problem lies in the fact the app starts with the login and then the root page needs to be changed to either the launcher or aquarium selector views - an experienced developer will solve this quite quickly I think.