The "November Criminals" was a collective term used to label the bureaucracy in charge during WWI, as well republican politicians in general and communists. The month of November was particularly significant, as it was during November 1918 that the armistice to end World War I was signed. Hitler despised these people so much because he believed their blunders cost Germany the war and placed undeserved war guilt on her. He also hated their subservient attitude towards paying reparations. Hitler was the first to really step up and say that the nation should ignore the reparations bill handed to her; he believed, and rightly so, that the continued payment of reparations would never result in Germany reaching her pre-war eminence. So, in essence, the "November Criminals", those same paper-pushers who'd caused Germany to lose the war, were now holding back Germany from achieving the greatness she deserved in Hitler and Germany's eyes.
Hitler also used the "November Criminals" as a scapegoat, rallying the middle-class behind his cause. He told the people what they wanted to hear - that the generals and bureaucracy lost them the war, not the German public or soldiers. Ex-servicemen took a particular liking to his views and volkisch philosophy.
The term "November Criminals" was used pretty much at the establishment of the Weimar Republic to refer to anyone who supported its creation, I'm not quite sure who coined the term though.
