It's likely just the adjustment, over time they will wear down a little bit and you have to adjust them in further. My brakes weren't working at all when I was tuning my MTB this year, so I just had to take an allen wrench and adjust the actual pad along with brake tension, and wallah, they work fine.
I would also suggest spraying some WD-40 where the cables pull in and out, sometimes they will get rusty and prevent a smooth pull.
PowderHound and TreeNinja
Last edited by HoboMaster; 05-15-2011 at 10:53 AM.