I just installed Ad Injection and set up one ad to appear at the bottom of my content. I have Jetpack installed and have enabled Infinite Scroll.
When I load my front page the single ad shows up at the bottom of my first blog post - great!
But when I scroll down to the end of the page, the infinite scroll loads with the spinning circle thing. When the content is loaded, the entire webpage is replaced with just my "bottom ad" which appears at the top left corner.
My current workaround is to disable in-content ads on my front page in which infinite scroll is enabled. It still displays fine on the individual pages/posts.