Hi, I have a lot of experience with Joomla and the set up of the back end system. Joomla is very flexible with style and layout and pretty much possible to do anything with it. There is an index.php and an index2.php and maybe the return link isn't picking up the index.php and going straight to index2.php. but more than likely the error is in the Menu section, where you have two separate menus going to 2 address's

If you want you I can take a look at it for you