Instructions
Turn on your Xbox 360 and insert the Grid game disc into the disc tray. Wait for it to initialize, and then scroll to the "My Xbox" menu and press "A" to start the game and begin playing it. If you at any time encounter a problem with the game or an "Unreadable disc" error message pops up onscreen, continue reading.
Remove Grid from the Xbox 360 disc tray and inspect the underside of the disc. If it appears smudged or dirty, dampen a soft washcloth or other cloth with water and wipe it off, starting at the center of the disk and wiping outwards. Do not wipe in a circular motion around the disc. Once it is sufficiently clean and the water has dried off, reinsert the disc and repeat Step 1. If you encounter another error, you still have one more option to try.
Go to the "My Xbox" menu, click "System Settings," choose "Memory," select your hard drive or other storage device, select "Games," scroll down to "Grid," select "Game Options," and then press "Delete." This will remove your saved game data, possibly eliminating your problem. Reinsert the game disc and attempt to play it once more. If you still encounter problems, your game disc is most likely damaged, meaning you need to get a new game disc in order to play Grid again.