Al Franken could not vote until July.  Kennedy died in August and the Dems lost the vote then.  Therefore that makes it a month (with the Arlen Spector - who else caucused with the Dems - was it Bernie?).  In any case, it really does not matter but in the end the argument that the Dems took no action is not true.  The Dems did try to deal with it under Obama with the gang of 8 (bipartisan) and the House Republicans would not even allow it to come up for a vote.  

You are true, the R's are not filibuster proof currently with 54 to 44 (with two independents).