I’ve found a number of references to the obscure error on the web:

Failure trying to run: chroot /target mount -t proc proc /proc

After careful diagnosis, I have come to the conclusion that this error has three causes (at least for me):

  1. A bad CD drive. [replace it]
  2. Bad CD-media or a badly written CD. [slow down the write, or change media]
  3. CD drive incorrectly connected (Cable Select, Master, Slave: incorrectly set) [check that cable and setting match, and that you have at least 1 Master connected, with the drive either set to CS or Master on a proper cable]

I hope posting this helps other people, as this problem took quite a while to diagnose, and much hair-pulling was involved. In my case, it was a “gradually” degrading CD drive (1), although I’ve also experienced (2).