When I preview in CC Cart Creator the header - everything about the nav buttons - is missing. I created a custom design in CC Cart Designer Pro and I have selected it as my theme. Any idea what's wrong?

Look in Designer Pro at the header properties. Look two boxes down and see if you have an image defined in that box for the header.

Also, a screen shot would be helpful if you have the ability to. Another test you can do is upload it and see if it appears live. CCSC can act funny sometimes in preview.

Yes, I do have an image defined. Not sure on the screen shot. Since I'm linking the the cart from VSD, I need to do more work on it before uploading....

OK. Try opening the blank theme in Designer pro, put a distinctive image for the header. Then go file and click save as theme. Open Cart Creator and it should be available for you to use. If that doesn't work, the most likely explanation is that Cart Creator is looking in the wrong place for it.