Basically the MoI PDF and AI8 importers are set up to try and deal with stuff that is often problematic from 2D vector illustration programs while the DXF importer doesn't, it's expecting the stuff in the .dxf file to have been drawn in a CAD program instead of in an illustration program.

So from CorelDraw you would want to use either PDF or AI version 8 file formats for transferring from Corel into MoI and that should work better.

- Michael