First off, you should probably tell people they need to link the comctl32.lib when compiling the program.

Your problem is located in WndProc, you'll want to find:

Code:
               mcs.szTitle = "DarkType Unsaved Document";
and change it to:

Code:
               mcs.szTitle = "[DarkType Unsaved Document]";
Since in your MDI child create message handler tries to load a file if the child window's title doesn't start with "[".

See:

Code:
         if(*szFileName != '[')
         {
            if(!LoadFile(hEdit, szFileName))
            {
               MessageBox(hwnd, "I Couldn't Load File.", "WHOA THERE!!! SETTLE DOWN!!!!",
                  MB_OK | MB_ICONEXCLAMATION);
               return -1; //cancel window creation
            }
         }
I tried the fix, and it sees to work now for me, so hope that helped.