You will need to delete your user obp file from your Bryce folder, then reimport your objs. This happens to me OFTEN on WIN98SE with Bryce 5. Everytime I import an obj and make it an obp I save out the newly created obp onto a cd. I use the obp user library to hold the models that I am currently working with and when I am done I delete the user obp freeing up my library for my next project.