hmm, I have the same problem on my website.... Also same problem is on www.digg.com empty box shows up and at the bottom it says "sponsored links". We have a website with 15 million page views per month so I hope google is just experimenting and is about to fix this problem... So both www.digg.com and forums.digitalpoint.com does not show any google ads for me currently, which is really strange...
I see google ads on all sites working fine... except DP... what is going on... did DP got ban frm google?