Try This...
Close All Open Apps... Sign Out of your Account... Perform a Reset... Try again...
Reset ( No Data will be Lost )
Press and Hold the Sleep/Wake Button and the Home Button at the Same Time...
Wait for the Apple logo to Appear...
Usually takes about 15 - 20 Seconds... ( But can take Longer...)
Release the Buttons...
Note:
Anything Downloaded with a Particular Apple ID is tied to that Apple ID and Cannot be Merged or Transferred to a Different Apple ID
Apple ID FAQs > http://support.apple.com/kb/HT5622