Back in Linux this morning and put the music disk in. Up comes the notifier and I play the songs with the VCL player. 
I put the picture disk in and look at the pictures. 
I put the DVD in and look at the DVD. 
What can I say? What ever there is to be said, I am pretty sure just19 will say it for me. 
(AS is too polite!) 
... mmmh... not really ... 
Not marking solved yet because not really sure what was done to solve it. 
I will wait until I can do it 3 times in a row.
In fact it's not solved... unless the media was put in the wrong side 3 times in a row 
The next time that you will be unable to access a CD/DVD try to reboot your computer (from Linux to Linux) and then try again.
Right now the only thing I can say... it's an intermittent issue... origin unknown. 
AS
Yes, it must be an intermittent issue.
Joble made a suggestion elsewhere to mount the CD. I have not done that yet. I thought I would try the procedure one more time first.
This AM when I first booted into Linux I immediately tried the 3 different disks and they all worked as I posted.
Then I tried the very same 3 disks after being on the computer for several hours. None of them played and I got the same results posted earlier. Nothing comes up. No notification boxes etc.
Next I rebooted back into Linux and immediately tried the 3 disks and they all play fine...except the music CD halts or stops for a second. This does not happen in Windows.
I did get thrown off by putting the media on wrong side in Windows.

It seems things only play after the initial boot. I did notice this happening months ago.
(This shouldn't happen.

Talking to myself.)
.