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Try a force shutdown.See how it goes after.
http://userguide.sonymobile.com/referrer.php?region=global-en&product=xperia-sp#!Turning-on-or-off-t...
I will wait.
Try settings-apps-all-nfc service,force stop and clear data.
Robson,do you have a tag to test NFC?It should show the icon if it is active.