502 bad gateway

I'm having the same issue on Google Nexus 4.  Over AT&T network I get the 502 Bad Gateway error, but if I turn on Wi-Fi, it will connect without issue.  

I have seen that some users are seeing this issue and calling their network providers to get it fixed. It seems to be a network issue. Are you still having issues?

This is probably due to your mobile operator http proxy on 3G, getting in the way and returning that error.

Google around for more info on http proxy and your mobile operator and android to get some instruction on how to remote it or change its settings (most of the tilme it is in hidden menus).