It wasn't something I did in Windows or the Control Panel, rather it was the Personal Firewall feature in the Norton Antivirus 2006 product. Here are excerpts of my online chat w/ the Symantec tech:
Tech: Diana, do you able to open them when you turn OFF Internet Worm Protection of Norton AntiVirus 2006?
Me: The exact feature I turned OFF was called Person Firewall. I'm not sure what you mean by Internet Worm Protection. Maybe they're the same thing, but that isn't what my Norton system called it.
Tech: Okay, fine.
Me: I open my Norton Antivirus program>click "Norton Protection Center">click the "web browsing" hyperlink>click the "Norton Personal Firewall" hyperlink, then click the message saying "Turn Norton Personal Firewall Off". Then I open iTunes and can get into the iTunes store like I used to be able to w/out doing all that.
Tech: 1. First we need to download and save the Norton Removal tool from
http://www.symantec.com/nrt and save it in your computer desktop.
2. Then, please run the tool and restart the computer.
Tech: 3. After this, please download and install Norton AntiVirus 2007 from
http://liveupdate.symantec.com/upgrade/NAV071420.exe
Tech: 4. Then, activate it with product key (my product key here)
I followed those instructions, which got me Norton AV '07 instead of '06 and now I'm fine.