I edited my thread posting but you answered first. I had added the comment:
"I did change the checkout button on the cart page to go through a SSL. That's probably the reason, so how would I make the Paypal button see the contents in the cart?"
Well, I did follow the documentation you're referring to, a few days ago, and it's been working fine for the on site checkout process, but not for the Paypal button. So I really still need to know how to get the Paypal button to see the cart contents.