The name and address that you have on your iTunes account match exactly (including format and spacing etc) the name and address that the card is registered to, and the card was issued by a bank in the same country as you and your iTunes are ? If not then try removing the card and re-entering its details : http://support.apple.com/kb/TS1646
If the issue persists, contact your credit card company and verify that they and any company they use to process credit card authorizations have the correct information on file.