1 1/2 hrs with tech support. Connection Failure with App Store Continues...

I would like to upgrade to OS X Mountain Lion. Currently, using OSX 10.7.5. I am able to log into iTunes. Problem solving: Tech walked me through: Cleared Cashe, Cookies, and Preferences. Firewall off. No Parental Control. No Anti Virus. Checked ID and Password. User is ADMIN, even tried a Test User. Tried to reinstall only the App Store Application to find out you have to Reinstalled Operating System. That done. I still have the same problem. Any thoughts or suggestions?