I encountered the same error message using the P4 patch to export a poser character (ultramorphwoman2) as a wavefront object. Turned out the the obj file written by poser had a size of zero bytes and when imported to bryce was obviously garbage. I was not able to resolve this export problem, but have been able to export poser characters and import them into bryce when they did'nt have many morph targets applied.

Does the patch happen to address the figure export problem (or feature loss)? In P3 you used to be able to export a figure as an object with all the body parts grouped, so when it was imported into bryce, there were only 14 (or so) texture map objects for a nude figure. Now when I export a P4 figure as an object, and import into bryce, I get well over 50 objects...Or am I just missing the proper way to export in P4???