Hi Bob,
As you know, I'm not a Mac or (normally) Safari user, but I get the black surround Lytebox on the image above in this thread.
I think, from memory, for the attached images thumbnails, I still get the older white/cream surround Lytebox, the one with "Prev" and "Next" buttons both on left hand side.
The black new one has left and right arrows for that use;
I just tried it with Safari 5.1.2 and it works fine (on my Windows 7 PC).
Not sure that's any help, but I can understand your frustration.
Cheers,