convert - Last edited information missing when used QGIS - Dxf to Shp

I am doing as constructed drawings which require the information to be in a GIS system and more specifically drainage as constructed drawings.

I must have a separate file for Pipes and Pits. First I use Autocad, save as a DXF then use Quantum GIS to convert the DXF to SHP. So the problem is that the last edited piece of information from the autocad file is missing when i convert it. I can go back and change the last edited line, polygon or polyline and the last thing touched will still be missing. Help?

I have looked on the QGIS website but haven't been able to find anything helpful.