The cable goes from the shifter, outwards and then down along the down tube. There's one secure spot for it along the downtube - it's held by a metal band with a plastic guide through it. I'm guessing that's the adjuster (cable stop) in question. I think I can adjust it upwards and take some of the slack out (I'll do it tomorrow, it's coming up on 22 here). Now the question is: How was it fine before but not now?

M.