I called Apple support today. This is what the solution they gave me is.
1- Download itunes 10.4.0.80 (the latest version of itunes)
2- while downloading it , Uninstall the old version of itunes you have (or just uninstall iTunes if you are already running 10.4.0.80
3- Uninstall Quicktime also
4- Uninstall Apple software update
5- Uninstall Apple mobile device support
6- Uninstall Bonjour
7- Uninstall Apple application support
8- Reinstall iTunes 10.4.0.80
Apple Tech said you HAVE to uninstall in this order. After I did this, the App Store started working correctly. The only question I have, is how could it do it to so many of us, on the same day. I have another computer in the same room as this one.. This morning, after I got off the phone with Apple, I turned it on, and low and behold, the same problem.. I think it's probably a bug in this version of iTunes. What ever, it works now, and now we know how to fix it.