Citat:
We don’t allow publishers to implement AdSense for content ads on interstitial pages. So if a user has decided to watch a video, you may not implement ads on pages saying “your video will start in 15 seconds." We’ve also seen this placement on Flash gaming sites in the form of an ad being shown to the user while the game is loading in the background. However, even if you allow users to skip these ads or close them, this placement is not allowed.
adsense.blogspot.com/2010/10/avoiding-accidental-clicks-pt-2-use.html