Error -3212 is "Permission Denied". And the interesting thing from your network diagnostics is that you're getting this just pinging www.apple.com, let alone the store.
What happens if you go to
http://www.apple.com with IE? Are you using IE or another browser? iTunes uses the IE settings for network access, but if you've never set up IE because you're using another browser like FireFox or Opera, you may not have IE set up.