Google has confirmed in a Google AdSense Help thread that many publishers did not received their January payments due to a bug in the system. The bug put publisher accounts on hold, which automatically held any payments being sent to these publishers. Google's AdSense Pro William confirmed the issue last night, saying:
Of late we have noticed complaints from Publishers about not receiving payments on time in spite of having no visible holds on the account. This was due to a bug which has been fixed and in the mean time we have been removing the holds manually and the publishers would be receiving the payments in the next payment cycle possible. Also, to be noted the holds removed between January 15 and February 15 will be reflected in payments issued at the end of February.
I believe this is a continuation of the story we covered a couple weeks ago named Google Confirms Not Paying Some AdSense Publishers. Let's add this to the list of recent bugs we have been noticing with Google in the past week, I think we are over 10 now.
Forum discussion at Google AdSense Help.
