Might the curves from the section be splines? Did you try to IGES the dwg out? I bet you have splines in there and DXF supposedly will not support splines over 3 degrees.
If you just need "something" viewable in ACAD, CGM the dwg out of NX then import the CGM back in and DXF out the CGM. ACAD ppl won't like the result but they'll be able to see everything (more than likely).
Tim Flater
NX Designer
NX 8.0.3.4
Win7 Pro x64 SP1
Intel Xeon 2.53 GHz 6GB RAM
NVIDIA Quadro 4000 2GB