I've heard of the problem, from what I've read apparrently Microsoft had such a huge demand when they were launching the system, they had to spread the DVD-ROM production between three different companies. I guess one of those companies did a shitty job, and their 1/3 is mainly to blame for the fuckups in the systems. The new 360 I got from Best Buy was a launch system, when I turned it on it thought the date was 11/22/05.
Unfortunately when I play COD3 the system freezes during loading screens, so Im going to BB for a new one today.
As far as your disc error, I would call MS support and see if you need a new system, that sounds like the beginning of bad things to come. I hope you have a replacement plan or are within the 1 year warranty to be safe.