FYI, I figured out a workaround.
At the boot prompt I typed:
install-gui hdi=scsi-ide
And it's now installing the packages.
(yaay!)
>Hi. I downloaded the ydl2.2 iso image, and I once again
>experienced the same issue : during the install process, the
>"installer was unable to mount the CD/DVD" right after I selected
>which keyboard type I have.
>
>
>
>(help)