You're very welcome.
The Kindle Previewer is a reasonably accurate tool for seeing how a Kindle ebook will look and behave on a Kindle 3, Kindle DX, and on the Kindle for iPad and iPhone apps. It's certainly a useful tool for checking that the formatting works the way you expect/intend it to. Just a case of being aware that the NCX TOC viewer is an inspection tool, and not something present in the actual Kindle device. The intermittent problem you're having with displaying a "Copyright" entry in the NCX is kind of bizarre - goodness knows what's causing it!