I recently had an experience where the student (who I also think was ADD) had a different excuse each week for why he didn't have his assignments turned in to me (one was that the hard drive with his papers on it were in his brother's truck, which was in another state, but that he would be back the following weekend, and it still took me several weeks to get all the assignments). Whether they were true or not, I finally caught him in one where "the computer and Internet at home were down, his father was threatening to kick him out of the house, etc." and I told him that he could have come to the computer lab on campus. He really didn't have a reply. I think it also got him to finally stop engaging with me in a manipulative way.