Mike,
here's a link to the DSL manager software i'm using: http://db.tt/9B2ATKiJ
It doesn't do much than to log the transfer volume, and display an icon in the tray.
On a clean (Apple-free) Win 7 system, install that, reboot, check it does display the upload and download transfers in the icon, and then install iTunes 10.4.x or/and 10.5 and see if the store can be accessed.
I place almost any bet it doesn't.
Then, after the netsh winsock reset and a reboot, the store will display, but the DSL manager will be functionless, it's LSPs having been kicked out of the chain.
That's now neither Firewall, AntiVirus, SpyWare/Malware protection or any other software of that kind - it's a simple I/O monitor. It MUST pass on ANY traffic, it CAN'T block anything - it just needs to monitor and log the throughput.
I think that should make clear the problem is in the way iTunes (and it's peripheric Apple components) are not hooking themselves in properly.
P.
P.S.
Here's my batch/command file and a .reg file for the Apple Software cleanup task (saves a lot of time):
http://db.tt/fX6S6pll