DVD Mounting Snag

[Dale Hoffman]

What would account for the following problem mounting a DVD disc?

I recently swapped an internal CD-ROM for a Pioneer DVR-106 in my 
G4-500 where I operate OS 10.2.8 and use Toast 5.2.1. Burning media 
is Memorex DVD-R 4X at 1X or 2X. When I tried to mount the disc on a 
new G5, I had to insert the disc twice. Another incident resulted in 
hanging the G5 but after restart the DVD mounted. I tried an older 
CD-DVD reader in a G4-450 and it would not read this latest DVD. The 
disc mounts fine on the machine it was burned on and on another G4 
with the same DVR-106 Pioneer mechanism.

I know the discs are rated at 4X but I have had failed verification 
on burns nearing full capacity.

DaleH