The glitch came to light yesterday and seems to mainly affect regions outside North America, specifically Australia. This process covers anyone who didn't get a code with a retail purchase of the game, however.
Per EA Sports, you should:
• Go to http://help.easports.com.
• Select: Email Us.
• You'll be prompted to login with your EA Account. If you have none, create one. It's free.
• Choose platform, game and category. In this case, your platform is PS3/360; your game is Madden NFL, Madden NFL 2010; and your category is Registration/Product Activation. See this example.
You may then continue with this either via email or through customer service chat support. In both cases, notify EA Sports that you purchased Madden NFL 10 and that the Online Franchise mode access code was missing from the back of the booklet. Include in the email, or have available for the chat, the email address linked to your EA Account login, and your Xbox Live Gamertag or PlayStation Network ID.
Chat support for Madden NFL 10 is available from 9 a.m. to 9 p.m. U.S. Central time.