Quote Originally Posted by Fog_Watch
The solution was to use KNOPPIX_V4.0.2. This booted the machine fine.
In many ways I find 4.02 to be superior to any of the 5.x discs. But the fact that a different disc, even a 4.02 one, does boot just reinforces the belief that the failing disc was likely made at high speed and that another one burnt at slower speed would likely boot as well. Of course, there can be other differences such as media quality, but speed of burn is the most common issue that we see here.