Hmmm... let me ponder it a bit -
That's really odd. The only difference is that we aren't sending the header.
It's odd - because $tbopen clearly opens some kind of table - I wonder where it gets that from?

Let me look at what might not be getting set if I'm not sending the header and see if I can figure this out.

Those table wrappers get me every time. I need to setup a test site for tablewrappers so that I can test stuff.

Although you are a good tester too.
