First of all try the 'fix nearly all problems' cure of powering down completely - i.e. press and hold the Power button until the slider control appears, accept the offer to power down, wait until the screen goes completely blank - a few seconds - then press and hold the Power button again until the white Apple logo appears. The iPad will then power up - it takes a few seconds again - and then you're back to the Home screen. See if the problem persists and get back to us if there's still a problem or let us know how you get on.
Tim