?Meaning of error "protocol unexpectedly quit" ?

I have booted 5.1.1 as a Live CD about 10 times on an old laptop. Sometimes, all goes well, but about a third of the time, error boxes pop up advising me that the "media protocol unexpectedly quit" or the "file protocol unexpectedly quit". When this happens, the icons for the hard drive and CD disappear from the desktop. The most recent time I booted up and this happened, I found that my sound was still functional and I could still mount and read both partitions on the hard drive.

I have not seen this error message booting with other Live CDs on this machine. In seeking info on this error, I have googled without finding a clear
discussion.

Since this distribution works better with this laptop than any other one I have tried, I would like to uncover what if anything I need to do about this, because I want to move to a poor man type install on the hard drive.

Thanks in advance.

Steve