I'm also having the exact same symptoms as mikeshark813.
I have a 160GB Slim Model PS3 - CECH-2501A that I purchased brand new in February of 2011. I also bought MW3 just over a month ago, brand new, and have been playing it on and off since then, and have had absolutely no issues with the game or my PS3 up until about 2 weeks ago.
The first time I get a disc read error it was in the middle of a multiplayer DM game, and it promptly flashed back to the main multiplayer menu/lobby with the disc read error popup.
Ok, no big deal, sometimes things happen... but then it happened again about 10 minutes later (near the end of another match), boom straight back to the lobby/menu.
Then it would happen, periodically, during random matches, random maps, and random times. Sometimes it would send me back to the lobby with the error popup, other times it would freeze my PS3 entirely and I have to eject the disc to reset the PS3.
So after about 3-4 days of getting the disc read errors and constant freezes, I decided that perhaps something was wrong with my PS3 and began doing testing.
Test #1; Is the Blu-Ray Drive dead or dieing?
- Tried playing several of my other games and soime bluray movies; Homefront, Crysis 2, Black Ops,etc all single player and multiplayer versions worked without a hitch, played them for hours at a time with no errors or freezes..
Conclusion: Blu-Ray drive is working just fine.
Test #2; Is the MW3 disc scratched, dirty, damaged, etc?
- Singeplayer works just fine, but can't play spec ops missions or anything online... hmm.
- Bought a new MW3 disc from GameStop, got home, completely reformatted my PS3, reinstalled all updates and game data from the new disc. Played an hour or so of multiplayer and bam! Disc read error again... ok so it's defintely not the disc.
- But, talked to tech support, they said they'd replace the disc, but since i just bought it and still had the receipt I just exchanged it at GameStop for a copy they told me was just delivered that week. Get home, played for another 20 mins or so and goddamn DRE again...
Conclusion; Definitely not the damn disc, unless all discs made since they started mass production are faulty...
Test #3; Is the PS3 OS broken or are there corrupted files??
- Ran the PS3 recovery menu, Restored File System, Rebuilt the Database, deleted the history from the PS3, deleted the cache and cookies from the PS3 internet browser, and also deleted and reinstalled the MW3 files (all files, saves and all) just for the hell of it.
- Tried playing MW3 online again, same bs...
Conclusion; Not my PS3's OS or corrupted data that I can tell...
Test #4; Is the PS3 Harddrive faulty, damaged, dead???
- Took my friend's PS3 HDD from his slim (same model as mine) and tried to run his copy of MW3 on it. And yes, his PS3 is running MW3 just fine, he says he's encoutered the disc error message maybe twice since he started playing a couple weeks ago but nothing like what I'm going through.
- Tested his copy of MW3 with his HDD in my PS3... disc error, disc error, freeze, freeze, gave up.
Conclusion; Seriously... I'm at a freakin loss here...
Overall Conclusion; NOT MY GODDAMN PS3, NOT THE OS, NOT THE HARDDRIVE, NOT THE BLURAY DRIVE, NOT THE MW3 DISC.... so what does that leave?