My iPad is constently doing the same and i couldn't get it to do anything or stop at first, but I find that getting it to shut down and reload/restart works best. Sometimes it works by just pressing and holding the lock button, then 'slide to power off' (this doesn't always work, so I also sometimes have to press the home button and the lock butten at the same time and hold them both down until it reloads/restarts
(I'm not sure if it will actually work on yours, but it's worth a try as it works on mine).