So I talked to an AdSense rep today and apparently the presence of nessie is algorithmic, part of the algorithm detects whether the button can be perceived as part of the site navigation. I had 2 large leaderboard ads, one at the top of the content and the other at the bottom and apparently nessie could be mistaken for a pagination button.
So the solution is to move the ads into the content so the arrows don't appear as part of any type of navigation. I've never really though about users mistaking the nessie arrow as pagination. It's the wrong color and too big to be part of my menus.
I've always believed that putting the ads around the content provides the user a better experience and that I was doing the users a favor by not having ads all in their face while they read. Apparently they loved the content so much that they would click the arrow, thinking it was the next page, but when they realized they clicked an ad they would close the ad window resulting in an invalid click.
I guess we're almost forced to put ads into the content to prevent the ads with nessie looking like navigation. Make your site look like crap but make more money doing it.
I hope this gives people some insight, it just frustrates me. I try to keep ads away from menus to prevent this situation.