I didn't know that existed either. As a side note, about 7 years ago, I bought a stack of no name blank DVD's from a vendor at a pc show. I used them in my Panasonic standalone DVD burner to burn tv shoes,clips,etc. I had a number of them not finalized, but when I tried to finalize them, the process would fail every time. I could only view them. Upon talking to the vendor, he advised me to look on the Panasonic site and see if they have a firmware update for the burner. He said it likely won't be easy to find and he was right. I found a firmware update for my machine buried under layers of menus. After upgrading the firmware, I was able to finalize the disks. I don't know if you are still using the same machine these disks were originally burned on, so you might want to check the burner's site and see if there is a firmware update which may allow it to read older disks if you are using a newer burner.
What SNGX1275 said concerning the dye's might just be the case. Unfortunately for us, the process to create home CD's and DVD's is different from the process used commercially which to me is a better method since I don't believe they use disks that have dyes like commercial ones do, just a master that has the high and flat spots which is then pressed to create thousands.
To me, it looks like the safest way to preserve pics,movies and documents would be to have copies on the pc, an external drive, and burned to a few quality name brand disk manufacturers and check them maybe every 2 years or so on the original burner (if available) and a newer machine.