I think I found a glitch in Blender 2.70.
I loaded the Brooklyn Bridge file and noticed the arches had been "deformed" as a mesh slightly.
I'm sure that this can fixed by remeshing the .dxf file of the arches.
But it's obviously a glitch in Blender. I tried saving the Brooklyn Bridge as an .obj and came up with the same distortion of the arch mesh.
.....Pondering chin...interesting. Perhaps I should install 2.7 on the baby computer and troubleshoot the dxf files from there before reinstalling 2.7 on the main computer.....
Btw, installed 2.69 back over 2.7 on my main computer....Just to be on the safe side....
And, 2.7 didn't update personalized settings....So that was a pain but maybe its because 2.7 has such a different UI.