Ram Modeler - Import DXF

When I try import a dxf file into RAM Modeler I receive an Error Opening File Message. I do not receive this error if I download the example found here:

http://communities.bentley.com/products/structural/structural_analysis___design/w/structural_analysis_and_design__wiki/3114.aspx

However if I open the example in AutoCAD then save it as a DXF (any year), then try to import it. It does not work and I receive the same error message. Any Ideas on why this happens?

Using AutoCAD 2014. 

Thanks