Well, after failing (again) to get the arm off, I found that the pulley came right off (not good), but in a way this is good. See, I think that if I take a piece of non-slip rubber and wedge it between the pulley and the shaft (it rotates, don't worry), and seeing as the inside is "grooved" (think 3-4 rings), maybe it will hold in place. And seeing as I have a four-dollar belt, the pulleys shot anyway, and it was a free mower, its worth a shot.