It only works to export an obj or 3ds or whatever if the mesh was originally in that format and was imported into Bryce. I've had something that was a 3ds imported into Bryce and tried to export as an obj and that crashed too. And, if any part of it was created in Bryce, it won't work. The only things that can be created in Bryce and then exported are terrains and lattices. And, unfortunately, Bryce won't export mats under any conditions I've ever heard of. Basically Bryce is designed to be the end-point, into which you import whatever else you are using and do the rendering, as far as I can tell.