...along with the good advice that stuartw has given, it's also good to try some of these immediate fixes as well as seen below.
1. Force the app to close.
2. Try to restart your iPad.
3. Try to do a reset.
Force the app to close down*by pushing the home button twice to bring up your multi-task bar. This will show all the apps that you have visited. By long pressing the app in question, it will begin to jiggle-press the red circle with the negative sign on the app. It will only quit the app and not delete. Than try to re-open the app and test out.
If that doesn't work, restart the iPad by pressing the power switch down to power off.
Third is to do a soft reset by holding the power switch and home button together until you see the apple logo. Hope that helps!