Probably caused by http://hub.qgis.org/issues/12314. Try downgrading matplotlib to 1.3.0. Cheers Rado -- View this message in context: http://osgeo-org.1560.x6.nabble.com/Processing-Toolbox-tp5315090p5315178.html Sent from the QGIS - User mailing list archive at Nabble.com.