Hi mumblebox.
I had the bad I/O with several Daz3d imports from Poser Pro into Bryce. There seem to be some errors in the original .OBJ files supplied with the models. If you can examine the final .OBJ listing in a good text editor (the files are quite large) you find many rows of vn ("vertex normals") figures. Each row should have vn followed by three numbers. Some rows can be corrupted i.e. they have a hash symbol # mixed up with the three values. Taking these out, e.g. by replacing the hash string with a space character seems to be O.K. and eliminates the I/O error.
I suspect that Daz, or the original model maker, has a dodgy compiler. BTW, Grouper does not help since the errors are in the model data and are just passed through.
Best regards, John