Do the first 2 steps first. Save step 3 as a last resort.
1. Force the app to close?
2. Try to restart your iPad?
3. Try to do a reset?
You can try this in order, if an app becomes funky.
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 reset by holding the power switch and home button together until you see the apple logo. Hope that helps!
Please see the replies after trying your suggestions:
1. Well, the I pad has been restarted several times since, so no luck on that. I shall try the other one.
2. Tried everything..... It says "the language is not available on the system" . Whatever that means!