A Google AdSense Help has confirmed reports from Google AdSense representatives that there was a minor bug on some web sites that did not allow the AdSense ads to be shown.
This publisher has a web site about music. But some of the music, he classifies as "hardcore" music. It is believed that Google felt the site was about hardcore pornography and thus automatically prevented the ads from displaying on his web site.
About a month ago, we discussed how Google AdSense has poison words that sometime prevent ads from being displayed. This seems to have been one of those cases, although, "hardcore" can be used in multiple ways, Google, in this case, felt it was about hardcore porn.
AdSensePro William said it was a bug and they fixed it, in this case. He said:
The issue was due to a minor tech glitch which is now fixed and the ads should begin displaying shortly. Please let us know if the issue persists.
I wonder if this was more of a global change and not a site specific change.
Forum discussion at Google AdSense Help.