Error #2025: The supplied DisplayObject must be a child of the caller.

Answer 1

Why is "DeviceLineChart" an <mx:Application>? If you aren't doing any fancy loading of sub-applications you might want to just change it to a <mx:Canvas> instead. If you do plan to load these dynamically you want to be looking at using Module Loader. What you are telling Flex is that there are two applications running inside your system, there are a few singletons like SystemManager that don't work when you use two applications without using a loading system to do it.