Yeah it's like I said in chat: When you first launch ISBoxer, it shows a path to Inner Space above the "welcome to ISBoxer" page. ISBoxer will be looking in that path for GameConfiguration.XML. If GameConfiguration.XML does not exist in that location, or is invalid XML, ISBoxer will give you that message.

So, first off, make sure ISBoxer has the right Inner Space folder in the box. If it doesn't, click the button to browse to the correct location.

And secondly, make sure GameConfiguration.XML exists in that folder. If you use Add Game and add something that wasn't there, and restart Inner Space and it is in the list again after restarting, then Inner Space is in fact storing GameConfiguration.XML. This would indicate that ISBoxer is pointing to the wrong Inner Space folder.