I guess she was just trying to show her "tough side" like with the IWR and Iranian votes. Another calculated vote perhaps?
Amendment to HR 5631
To Protect Civilian lives from unexploded cluster munitions.
Sec. 8109. No funds appropriated or otherwise made available by this Act my be obligated or expended to acquire, utilize, sell, or transfer any cluster munition unless the rules of engagement applicable to the cluster munition ensure that the cluster munition will not be used in or near any concentrated population of civilians, whether permanent or temporary, including inhabited parts of cities or villages, camps or columns of refugees or evacuees, or camps or groups of nomads.
Obama voted for the ban along with 29 other Democrats on September 6, 2006. Roll call for the vote.