I'm having the same issue, got back from a week vacation and "BOOM" my iPhone won't sync with Outlook Calendar, so I reinstalled iTunes and though my login ID and password are correct and work getting into iTunes store via my iPhone.
I can download apps there, but can't sync them with iTunes because whenever I try to Authenticate my computer or try to login to iTunes Store via my computer, I get the error message: *"We could not complete your iTunes Store request. The network connection was reset. Make sure your network connection is active and try again."*
Clearly the network connect IS active because I can peruse the iTunes store via iTunes, and have full internet access via browsers... so what's the fix??
I spent an hour with a junior Apple support guy just now and all he did was have me go through all the same stuff I already did.
HELP iTUNES SUPPORT PEOPLE!!!