DoubleClick ads only display when cookies cleared. How do I fix this?

I'm not sure if we have any DoubleClick experts around or not, but I seem to have a problem with ads only displaying on my website on the first visit. If you visit the homepage, for instance, the ads will show, and then if you click an article, they will not. They will, however, display if you refresh the page.

I'm using DoubleClick, and have tried turning Super Cache off, but to no avail.

Anyone have a similar problem, or have any insights as to how I might rectify this?