As I understand it, dxf comes in a range of format types. QGIS (v2.0 'Dufour') can export any layer to a dxf file. However I have a hydraulic modelling package which relies upon importing the dxf file as the R12 format.
This import does not seem to work. I was wondering which dxf format does QGIS export to? If it is not R12, this may be the reason why this is not working.