Bizarre amazon ads + adsense issue

This is really odd. I've had a 3 adsense + 2 amazon ad set up for my blog for months. Yesterday I updated an amazon ad from black friday to cyber monday with this code

<iframe src="http://rcm-na.amazon-adsystem.com/e/cm?t=thetodlif-20&o=1&p=26&l=ur1&    
category=cyber2014&banner=1PY6R9RS79W616ZWVZ02&f=ifr&linkID=VF3A62ZEBVVFLT62" 
width="468" height="60" scrolling="no" border="0" marginwidth="0" style="border:none;" 
frameborder="0">

1 amazon ad and 1 adsense code are on all posts (beginning and end) then the other 2 adsense and 1 amazon are in the side bar of the main side so appear on pages and posts. Meaning at any given time there is no more than 3 adsense ads, 2 on pages, 3 on posts. Well, after I switched to the ad code above the sidebar ads vanished on posts. I eventually experimented with just removing the new amazon code from the end of posts and presto, adsense in the sidebar is back. It appears they are removing the sidebar ads because the amazon ad is being viewed as adsene and putting it over the 3 ad limit.

Why would google be seeing this amazon ad as an adsense ad?