I have a problem with Piwik 2.0.1 and 2.0.2 to generate monthly figures for December 2013. In the date range I choose Month and December 2013 and get "There is no data for this report."
This work for all other months as well as January 2014.
I get figures in daily and weekly reports for December 2013, though. So there is data in the DB. A manual look in piwik_archive_numeric_2013_12 showed as well that there is data for December 2013.
Most likely a temporary archive issue. Try deleting the month table for this archive (in the DB, both _blob and _numeric tables). See: http://piwik.org/faq/how-to/faq_59/