I haven’t tried that yet – I would need to strip the ad and then get people to email me if it reoccurred.
However, if that is driving the issue, it must be a WP problem in the way 3.6 is rendering JS because nothing else has changed with the way the ads are delivered.
Whilst my top ad is from an agency, it is also impacting the below the fold ads (supplied by Google) because my click through rate has gone crazy.