Update: This issue is now marked as “RESOLVED”. Here’s the official word:

Update (11am, August 31): The issue with our notification system has been resolved. If you’re still seeing an alert in your account that you have rejected ad requests, please follow the instructions in the Help Center article linked from that alert to resolve the issue. Thanks for your patience as we resolved this.

Google apparently has some issues with AdSense after recent system changes.

Several site owners – including myself – are getting a strange error related to AdSense in the Google AdSense administration panel:

You have rejected ad requests, which will result in lost revenue. See details.

Do not change your AdSense ad code because of this rejected ad requests issue!

This is a system glitch that Google will correct.

Google has recognized and added the issue to their “Known Issues” list with the following description:

“Some accounts incorrectly notified about rejected ad requests”

We recently changed the way our system surfaces alerts related to rejected ad requests. This has resulted in some publishers seeing an alert in their AdSense accounts about needing to fix rejected ad requests, though no action is required on their part.

We’re quickly working to fix this so that only publishers who need to take action will see the alert. We hope to have this resolved in the next couple of days, and we’ll update the known issues page when the update is live. If you are concerned about this alert, please check your account after that, and if you still see the notice, follow the instructions in the Help Center to resolve the issue. Note that the vast majority (over 90%) of publishers now seeing this notification will not see it after the fix. If the instructions in the Help Center don’t seem to apply to you, you are probably one of the publishers who should not be seeing this alert notification.

Thank you for your patience as we resolve this issue with our notification system.”

If you click on the “See details” link, you’re taken to a page which shows which ad units have been rejected. This reads:

The errors listed below will result in blank ads being displayed on affected pages starting August 15, 2012. Please make sure that you fix these errors before then.”

AdSense Rejected Ad Requests Details Page Example from TommyNation.com