Many Officejet 6500 users, with many posts, relating to this exact problem, or very similar. All HP responses have just linked back to the same trouble shooting steps, that everyone has already tried. This is the one, and only, post I have seen, that may actually get at the real problem.
In my call, today, I requested HP Tech Support review this specific post, and, if confirmed, reference the problem (and possible solution) as an option, in addition to the standard trouble shoot & resolve links.