Thought I'd share my experiences here in the hopes that it might help someone else. Today I flashed my new samsung ms28 with the xtreme 5.2b firmware (plays backups at 4 speed) and almost no backups would play, kept getting the dirty disk error (so although it was seeing it as a game (i wasn't getting the unrecognizable disk notice) it couldn't read the data). Even the games that did load, crashed (froze or just showed black screen) after a few minutes of play. I was totally puzzled. Anyway I flashed the original back then reflashed with 5.2c (plays backups at 12 speed) and everything runs like a dream now, all disks load and play with no errors whatsoever. All i can assume is that 4 speed is too slow and doesn't load quick enough so the 360 shows the error of dirty disk? Hope this might help someone with a similar problem.