Tom, the problem seems to be related with the K2 theme you are using (and not WordPress), which generates the posts through javascript — thus no request for ads is sent to google when using the timeline slider.

In general, I think this is not a good idea to use such sliders from the point of accessibility and usability, although it may seem a nice “feature”. I don’t know if you have an option turn this navigation off, but I suggest you take a look and decide yourself.