Funky Pioneer 106 behavior

[DeadLily]

It's only a year old, and it's acting wierd with one particular disk. I'm comparing it to another nearly identical disk. Both are the same media (Ritek G05), both work on my Mac Mini's internal drive, both play fine in my standard DVD player, both were burned within the same week with this same 106 drive. However, the 106 will not mount one of the disks on the desktop. It examines it for a minute and spits it out. The other disk it mounts okay.

Like I said, the 106 burned and verified this disk, and it works on everything else. Is the drive going bad?

(G4 Mac Mini, 10.3.9)

[terryj]

Is the disc heavily scratched on the underside?
Does it mount in another Computer ( Mac or PC)?
Is the bad disc in question have a printed top, a label,
or something Physically different from your other discs?

and last, did it and the one that plays both come out of the same spindle, or were seperate single packed dvds?

[DeadLily]

It is not scratched. It came from the same spindle as the other disk. Physically they are identical. They are both inkjet printable, with virtually the same pattern printed on both. And the odd disk DOES mount on the same computer through the internal drive, but doesn't mount through the 106.

As I said, the only odd behavior comes with the external drive, yet that drive has no problem with the other disk.