Our servers were not able to detect the “cd rom” (the error message said something along the lines of cd rom could not find the ‘release’ files) while installing ubuntu 12.04 server edition from a flash drive using either YUMI or Universal USB Installer

  1. Hit F1 during error message
  2. Mount the ISO
  3. Symbolic link the ISO
  4. Hit Alt-F1
  5. Continue (Don’t check disk for defects as this will force you to link it again for some reason)
This works for YUMI and the other booters.

source:
http://demtrex.wordpress.com/2011/04/04/work-around-the-cd-rom-detection-issue-when-installing-ubuntu-server/