As of spring 2013 at the earliest, the NIH will begin to hold processing of non-competing continuation awards if publications arising from grant awards are not in compliance with the public access policy.
Please read this blog post by Dr. Sally Rockey, NIH's deputy director for extramural research.
We are committed to doing all we can to help our grantees ensure they comply with the policy. This summer we made it easier for project leaders and the authors they support to collaborate in the paper submission process through enhancements to My NCBI. We are giving funded organizations at least five months to prepare for our new process, and we hope you use this time to assure that publications are in compliance with the policy long before this change in process begins.