This should probably be in the Adsense forum.. they may be better suited to help you out.
There are several possibilities. Are your ads displaying on any of your websites / pages? If you're banned from adsense I imagine you would see something like this, however you would not have ads on any of your sites. Another possibility is that your domain name could have been banned by adsense. I have a domain name that I registered about 2 years ago and it was blacklisted by adsense and I have been unsuccessful in getting adsense restored to it.
Most likely, however, is that the adsense code is getting messed up. Did you install any plugins recently? Have you messed with your adsense code at all? I would check and make sure the code is complete by re-adding it all to your site and see if that takes care of the problem.
I used to know of an online tool that you would simply enter your domain name and it would tell you if your site is blacklisted. Try searching Google for it.
If you have ads displaying on different sites / pages, then it is either the Google code or something on those specific pages that's messing it up.
Is this a WordPress website?
If you want more hands-on help PM me. I can take a look at your domain and the code myself for you.