Here is David Hardy's blog post on it...unlike one of the commentors to his blog, I am thinking that the Senate tagged the gun rights amendment to the bill to ASSURE its passage in the House. Back in the summer a bill was overwhelmingly passed in the house to restore gun rights to D.C. The DEMS really really want DC to have a representative. It's another DEM vote in the house.
http://armsandthelaw.com/archives/2009/02/a_curious_day_i.php