For me
it happen to iPad 2nd when I purchase a "stack of coin"
in 'Pixel Gun 3D' $2.99
( 04/19/2015 11:00 AM. )
i did
Settings>General>Restrictions>In-App Purchases>On
Then.,
1. I keep click cancel real quick / as fast as possible
2. it will disappear for 1 or 2 second
and it will come back , you have to keep doing it
don't give up
3. Then you have to click on Setting real quick as fast as you can
4. ( if the asking question come back , don't give up , keep do it quick )
5.
setting -> reset -> Erase All content and Setting.
then follow with.
setting -> reset -> network setting.
Then my iPad 2nd come back to normal.
I'm not garuntee anything at all ,it will work for you
or will not work for you. But it work for me ( and the
thing why I dare to do that because I back up my
ipad with my laptop frequently )