I can make a good guess. It's the part I put in bold. That crack did do harm. A cracked disc is on its deathbed: eventually all the spinning will cause it to grow until the disc is no longer one piece anymore. I had the same thing happen with a copy of Yuri's Revenge once. All of a sudden the game freezes, so I had to reset my computer and then the disc can't be read. I open the drive and here's my disc in pieces.cgmetallica1981 said:So I'm getting ready to play some good ol' Modern Warfare 2 (Haters gonna hate). Take the disc out of the case, seems normal except for all the minor scratches it has gained over the last year. I have it installed to the hard drive so those scratches aren't a problem. Over time, the disc has gained cracks in the useless plastic part in the very middle of the disc that did no harm either. I put the disc in, it's read by the 360, and I play private match for about 45 minutes. We decide to play online and that's when I get an "unreadable disc" error. I check the disc and it has a crack halfway through it. The 360's on a balanced, flat surface and is laying vertically. I also payed $100 to get this thing repaired about a month ago. I honestly don't know what could of caused this other than the console itself.
And yes, your disc wasn't spinning that much because the game was installed, but still, it is checked on start-up and eventually that's going to do it. It's not the 360's fault, that'd happen to any cracked disc in any disc reader. Just be glad the 360 has a tray instead of those awful auto-feeding things that the PS3 and Wii use so you could just open the tray and remove the pieces rather than have to send it off for repairs or dismantle the console and then disc drive yourself.