HT1918 Security Code Problems

Question

Why would my credit card security code all of a sudden become "invalid?"  This is the same card I've used for 2 years.

Answer 1

This message is a catch-all for any billing anomaly.
Be sure you are using a valid credit (not debit) card.
iTunes Store: My credit card's security code or zip code does not match my bank's records
This is what Apple says in the above: http://support.apple.com/kb/TS1646
In most cases, this issue is caused by a formatting error in the billing address that you have provided. You can correct the issue by verifying that the information you have provided is correct, or by changing the format of your address to match the format that your credit card company has on file.
You can verify and/or modify your billing address by following these instructions:
Open iTunes.  If you are signed in to iTunes, skip to step 4.Note: Verify that you are signed in to the correct iTunes account. If you are unsure which account you're signed into, choose Store > Sign Out and proceed to step 2.
Choose Store > Sign In.
Enter your account name and password, then click the Sign In button.
Choose Store > View My Account.
Click the Edit Payment Information button.
In the Payment Method section, choose None.
Click the Done button at the bottom of the page.
Click the Edit Payment Information button again.
Enter your billing address exactly as it appears on your credit card statement.
Select your credit card type in the Payment Method section.
Enter your credit card information, your card's security code, and the expiration date.
Click the Done button at the bottom of the page.
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.