I'm one of the people suffering from the "Unreadable disc" issue when starting up the game (before the title screen). I can get around this by removing my HDD and using a flash drive to play. Ok, no problem.
However, now I'm running into another issue where, randomly at certain checkpoints in the campaign (the ones that create a continue point from the lobby, for example: Rally Point - Charlie), my screen goes black and I see these forerunner symbols changing rapidly on the bottom right. After a few seconds, it returns to the title screen, forcing me to replay up to that point to either continue or run into the same problem.
So far I've played from Rally Point - Charlie up to the point where you first get the Mantis and every time I either approach or try to enter it, the black screen with symbols appears and kicks me from the campaign.
Has anyone run into this issue and know of a fix? This is becoming very frustrating.
Note: I've tried clearing the cache on my HDD and it didn't help. Also, every other game works perfectly (Gears of War Judgement, Battlefield 3, etc.) and I don't run into any issues with or without the HDD connected. I've also patched to the latest update from 343.