yeah, i'm using bryce 4.0, and i've had that happen to me too. it acts like it's loading the scene, gets to the point where the wireframes should pop up, and then it reverts to the default scene and gives that damned error message. the only solution i've found is to save big projects twice, with different filenames, so you have a backup copy. otherwise you just grit your teeth, clench your fists, and try like hell not to punch the screen as you start over from the beginning.