DXF import is not working

[ghbanta]

I need to import DXF files into Inventor Professional 2012 SP2 with the aim of generting toolpaths in InventorCAM. I have been struggling for days with no success. 

The DXF files are topgographic map surfaces that will be CNC milled to produce landform models. The DXF files produced by the source program (Global Mapper) successfully and quckly import into Vectric Cut3d and are successfully produciing toolpaths. (see jpg file)

Inventor's behavior is very erratic but sometimes I am successful at getting the preview window in Layers and Objects Import options to show the part. (see Layers ... jpg file)

But at the Import Destination Options and beyond the process always fails. I have tried various settings with no success including just choosing a Repair Import. What happens after that is a the Part1 window appears and begins "Executing Data Import" and the green progress bar crawls to about 20% and stops. TaskMgr says the program is "Running" but it stalls here permanently.

Please help

Gary