Sorry, Walter, but I can’t replicate your problem. I just tried it with both a commercial disk, & one that I authored, & both mount & play normally.
I’m working with a G5 Dual 2.5 (not dual core, the ‘old’ one from last spring), QT 7.1, OS 10.4.6 & 3.5 GB of RAM.
Arnie
https://www.arniepix.com