Odd DVD player issue

First off apologies if this is in the wrong place or answered elsewhere but its my first post on the forum.

The problem I have is that my DVD player has stopped reading DVD-RW's that I make. For some reason it still reads and plays those which were burned 2 weeks ago and before but none that were burned since then. All the discs are burned on the same recorder and are all Verbatim 4x DVD-RWs. I have opened the contents of both those discs that work and those that don't and all the files have the same names etc.

Anyone any ideas as to why this might be happening?

My DVD player did this too. Spontaneously, it just stopped playing newly burnt discs - older ones were not a problem for the most part, just the newer ones. I tried burning them with a different burner, different type of discs, etc, but nothing ultimately fixed the problem until I purchased a new DVD player.

I can only theorize that DVD players become less sensitive over time, but I'm sure there's a better explanation for it.

I've just tried the same discs in both my MacBook and my xbox and the same things happen there. I can only assume that its the discs.

Just checked the info on the discs and it says that the old ones are "Universal Disc Format" whereas the new ones are "ISO 9660" format. I have no idea what these mean or if they are relevant. Do Macs have an issue with ISO 9660?