hi

I'd experienced d same problem when remastering n figured out that this problem occurs when their is logical problem in d syntax: -
U've Given

"mkisofs -R -U /mnt/sda1 | create_compressed_fs - 65536 > /mnt/sda2/remaster/KNOPPIX_CD/KNOPPIX"

in d source from which u r gonna re-master u've given /mnt/sda1 but it should b d root directory of ur source i.e some what like...
/mnt/sda1/source/KNOPPIX

on my system i used d following command: -

mkisofs -R /mnt/sda5/source/KNOPPIX | create_compressed_fs -b - 65536 > /mnt/sda5/master/KNOPPIX/KNOPPIX

this works!