Well, you could have one of two things going on.
1. No matter what anyone says, running backups WILL put an extra strain on your 360's DVD drive.But...replacing the DVD lens is pretty easy and kinda cheap.
2. Your Burner is beginning to wear out.I had several of my games that worked before but suddenly stopped working,but before I replaced my 360's DVD lens I reburned the games on a different Drive and they played just fine.Seems my Burner was at fault which at the time I was using Pioneers and I soon found out they had a very short lifespan.If I played them right after I burned them they played fine,but if they sat for a while I would get the "Play DVD" message or "unable to read disc".The sad part was the Pioneers gave no indication of when they began to die unless you burned a movie and if it skipped you new it was dying.
Hopes this helps.
This post has been edited by BanditRW: Jun 20 2012, 06:03 AM