Vellum????

You can try Intellicad which seems to open most everything, ever corrupt acad files and writes dwg files. MR

week 18/2003- 01 Ashlar Vellum Graphite v7.2 R2
week 12/2003-02 Ashlar-Vellum Cobalt v6.2-
week 05/2003 - 01 ASHLAR VELLUM COBALT V5.4
week 45/2002 - 02 ASHLAR VELLUM ARGON V5.2 ASHLAR VELLUM COBALT V5.2 ASHLAR VELLUM NEON V5.2 ASHLAR VELLUM XENON V5.2
email me, please

Vellum 2.7 was available for Mac and Win31. It was pretty easy to use and learn, did nice wireframe 3D and had dynamic object snaps, or hints, before anyone else. It did decent translation back and forth via DXF, with the exception of some glitches in dimension text.
I think it was version 4 that required 48Mb of _video_ ram to run on a Mac, which is when even my Mac fiend friends gave up on it.
Anyway, v2.7 could export DXF or IGES. I don't much care for IGES if there's a choice, but there's also a fair selection of free utilities to help you clean up damaged IGES files, so it may work as an intermediate format for you.
-Mike-

One claim to fame for VELLUM is that Burt Rutan, the famous aircraft designer likes to proclaim far and wide that this is his exclusive CAD choice. It seems to be well suited to the sort of free-flowing, organic wing shapes his firm produces - something for which AutoCad is ill suited.
I've never heard of anyone else using it, and I'm thankful I don't have to try to work with anyone who does.
G Faris