When using Xcode’s Archives panel to Distribute to iTunes Connect, I got this error:
The certificate for this server is invalid. You might be connecting to a server that is pretending to be “contentdelivery.itunes.apple.com” which could put your confidential information at risk.
Then I opened iTunes Connect in Safari and found that lots of images wouldn’t load and scripts wouldn’t run either. I captured the browser requests and found that a certificate for itc.mzstatic.com had a security problem and looked like a forgery. At first I thought it was because I’d bound some hosts entries, but after restoring DNS to the default it was fine — turns out it was FastApple’s DNS causing the problem. I’ve now switched to 114.114.114.114.
BTW, on OSX, GameCenter failing to connect to the server is also DNS-related. I’d previously bound 127.0.0.1 ocsp.spo1.verisign.com and 127.0.0.1 crl.verisign.net in hosts — just remove them.