My Ads unit shows Public service ads. What is Public service ads ? only one add shows on my web page.
About Public service ads you can click here https://www.google.com/adsense/support/bin/answer.py?hl=en&answer=32745 You had better contact google asap
While waiting, you can also add contents on your blog. By the way, may we know how old is your blog and how many posts are there?
It happens some times, even on my most popular site. Just wait and they will go away after a while. Sometimes it might take a few days sometimes only a few hours.