Just a thought.  Sometimes there is just one small item in a scene which can cause the type of Save/Open problems you describe.  Just for an experiment, you might try removing one item at a time until you can Save/Open successfully.  Sometimes it is something you least suspect.  The last removed item would be the one which is causing the inconsistancy.  Carefully reviewing that item in an isolated instance of Bryce may reveal what problem is.  Often it has to do with transparent/hidden attributes.  I hope you don't give up.  It may be something simple. ;)