I was noticing some issues with Ad Injection which we have been using for quite some time. Things started not working such as if we wanted to inject an ad after the 4th paragraph, it would not inject the ad, and it would hide the first 3 paragraphs. That was on on WordPress 3.5.2.
Tried upgrading to 3.6, did not help.
Tried moving the site to wpengine (different host, something we were doing anyway) Now the settings do not even load over there from within wp admin. Instead when we click on Settings>Ad Injection it returns a 502 Gateway error.