Hi there,
That would be because "2012" is a reserved term, for your yearly archives.
Examples:
* All of 2012: http://doublehockeysticks.com/2012/
* All of 2011: http://doublehockeysticks.com/2011/
* March 2011: http://doublehockeysticks.com/2011/03
http://doublehockeysticks.com/twenty-twelve/ would work, if you want. :)