What may surprise you is that it may not be an obvious Quickbooks module that is accessing the automatic updates,so you may still have missed the right setting. I would instead suggest that you just reset the firewall and allow Norton to recreate all the Smart Firewall rules as programs access the internet.
It still could be an Intuit issue. Did you do a reinstall of the Quickbooks? There could have been some corruption of either program, Quickbooks or Norton, that could even be caused by a hardware issue.