I finally found what appears to be a permant fix. Like most of you, I struggled for weeks to understand why I kept getting 'unreadable' or 'unrecognizable' errors with my BF4 disc. For the record, I have an original XBox 360 (white) w external 20 GB HD. I purchased the game new in late October and played quite a bit with few issues other than spotty EA server crashes. (I could never, however, complete a full round of DawnBreaker, and would suffer a full freeze requiring re-boot). But around a month ago, the 'unreadable' errors started, either mid game play, or at initial startup. I tried everything short of taking my 360 apart and cleaning the lens. I purchased 3 new discs, cleared the cache, reformatted my HD, tried to download the game to HD (never got past 50% without error). Nothing worked.
I was on my way to trade in my original 360 for another original 360 when one of the GameStop guys told me that data-intensive games such BF4 do not work well on the original 360s, and suggested I upgrade to 360 Slim.
So as of yesterday, after a quick install of my refurbished Slim w built in 250 GB HD, I have played BF4 without a single issue; no errors, no screen freeze, no re-boot. I even played several full rounds of DawnBreaker, which is a first. Game load is far faster as well.
Not sure this will work for all, but for those of you w original 360's, you would do well to consider upgrading to a Slim. Good luck.