OK, thanks. I'll make a couple of suggestions, although I don't know what is going wrong here:

There is a small chance that you are having optical drive problems because of DMA issues. I would have expected that this hardware would support DMA on the optical drive just fine, but you can try typing knoppix nodma at the boot prompt and see if that helps.

You have enough memory that you could load all of Knoppix into memory. I don't know if that will bypass the error or not, since it obviously has to read the disc to do this, but since the boot is starting OK, it might. Try typing knoppix toram at the boot prompt.