For CAD, the only thing I've ever had success reading dxf (no dwg support last I tried) with is QCad. It was a bit clunky I thought, but then again I don't do a lot of 2D stuff anymore so it might just be me. At work we use Solidworks, which is Windows only.
You might poke around the
MythTV wiki to get your nova card working.
EDIT: I also blundered across
this DWG viewer for linux. Not sure if it works...