Mon Aug 20, 2012 1:10 pm
If there are no scratches, dirt, or fingerprints, and it used to play fine on the same player, I'd be inclined to think it's the player starting to become more sensitive to DVDs being authored, recorded, and pressed just exactly right. My first stand-alone DVD player (about 12 years old now) started doing this several years ago, and now does it so often I rarely use it. I tend to use this player to check my own home-burned DVDs, and if it will play them from beginning to end the disc usually play on pretty much any other player.
Note that DVDs (and Blu-rays) play from the inside of the disc to the outside edge, and the dispersion of the dye layer on DVD-Rs is more likely to have issues from the middle to the outer edge, so these problems are most likely to show up halfway through or more. The same disc may still play fine in newer players that are more tolerant to disc and encoding anomalies. If not, then it's definitely a disc problem of some sort.
Some manufactured pressed discs have similar problems, more often from certain distributors (or authoring firms or replicators) than others. For example, many of my Kino discs won't play on my oldest players but look beautiful on the newer ones.