Error 1046 - Very Strange Problem

I am having a strange error that I do not understand and have not come across before. I have an Application (Application.swf) that is loaded by another file (Loader.swf), if I compile Application.swf by itself then there is no problem and the appropriate MovieClip from the library gets intstantiated and added to the stage no problem. However, once I compile the Loader.swf a 1046 Error is thrown saying ‘Type was not found or was not a compile time constant.’ Said Class is only instantiated in the Application.swf.

Any guidance greatly appreciated.