Did you manually add the .BR6 extension when saving? If you double click or drag 'n drop a Mac Bryce file without the extension it just loads the default scene. The only way to open a Mac Bryce scene without the extension is with the "Open" menu item. And the incremental save feature doesn't work on the Mac anymore 'cuase it ups the extension (i.e. br7, br8, etc.) instead of the file name.