On a somewhat related note, I've noticed that on all of the Telarc SACD's that I own, there's a statement to NEVER use a liquid-based cleaner on the disc. I have no idea why that should be, but it's definitely there, as plain as can be.

One of my most recent purchases (Beethoven's 9th on the BIS label with the Minnesota Orchestra and Chorale) all but refused to play when I first put it into my Marantz SA-8001. I kept getting a "no disc" display, even though there was a disc in the machine. I examined the disc, but saw no visible imperfections, and then lightly rubbed it with a clean cloth, and put it back into the player. And guess what? It worked just fine, and still does.