Chris from the Google AdSense team posted in the Google AdSense Help forum that there is a bug with some publishers seeing that their AdSense payments are on hold.
Some of you may be seeing an alert on your home page that your payments are on hold. I believe there was an error on our side that has caused this message to be surfaced for a number of publishers incorrectly. I apologize for any inconvenience.
We're working to resolve the issue, and hopefully this message will be removed soon.
About ten days ago we reported on earnings report issues within AdSense.
I am not sure if this is related, but it seems like some publishers are having this payment on hold issue now.
There is not estimated time for a fix.
Forum discussion at Google AdSense Help.