There is an extremely large thread at Google AdSense Help group with publishers complaining that they have not received payment this month from Google.
Jennifer, a Google AdSense representative, confirmed that Google did not pay some publishers due to a bug of some sort. She said:
We've been monitoring this thread and I can confirm that we have an issue on our back end that is preventing some publishers from seeing payment holds on their accounts. We are working with the YouTube team to get this issue resolved as quickly as possible. In the meantime, we have been working to contact affected publishers individually. Thank you all for posting in the forum. The faster we can aggregate data on a possible bug, the faster we can fix it, and forum threads like this are hugely helpful in surfacing these issues.
We appreciate your patience, and I assure you that we hear you and are taking this issue seriously.
Jennifer makes it sound like this is just impacting YouTube partners, but I am not too sure about that.
Google is known to have made many mistakes paying publishers in the past.
Forum discussion at Google AdSense Help.