I have the same errors every time I boot with knoppix.img.
I can't apt-get install anything now - I think the package indexes are corrupt.
This has happened on more than one computer/image file
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cat /proc/mounts
shows /UNIONFS twice! once with /ramdisk, once with /KNOPPIX.IMG
df shows /UNIONFS as 600M (the size of the image file) but the DVD is 10+Gig uncompressed
A second computer won't apt-get install now. Haven't tried it on the third one yet.

These computers are all rock-steady - all run stable over 1 week (one over a month) w/o image. DVD.iso on HD.
All ran memtest for days, mprime torture test for days, no errors.
All 3 are on UPS power.

apt-get on one says bad dpkg db, one says directory does not exist during unpack.
Knop4 never had any trouble with image files IIRC