Knoppix + Qemu-ed SL images. Detailed explaination

Hi everybody.
I'm writing to search for help about a problem i'm experiencing.
I'm using knoppix as host system for a virtualized computing-grid testbed, implemented as two Scientific Linux (RHEL like) guests launched by the qemu emulator.
Two scenarios follow:
1) I boot a Knoppix "vanilla" system (which get access, when ready, to the local disks). As the system become ready, I install qemu, uml-utilites,bridge-utils (via apt-get), and I run qemu to virtualize two pre-installed Scientific Linux images (laying on my main physical disc). Everything goes ok.
2) I remaster Knoppix to include qemu/bridge-utils/uml-utilites and the two SL images. When finished, I restart the whole system and boot from the new, remastered, knoppix DVD. When the booting phase ends, I try to launch my qemu-ed images. Both of the images, when trying to chroot to /, fail with a bad kernel panic (with a different initial message).
Does someone know what is the reason for this to happen? Why this behaviour difference within the two previous environments?
I've to precise that both images are "mirrored": they have the same OS and Filesystem installed on.
Thank you in advance,
Alex.

N.B: Kernel Panic detailed messages are as it follows:

<FIRST RUNNED IMAGE>

Redhat nash version 4.2.1.8 starting
Mounted /proc filesystem
Mounting sysfs
Creating /dev
Starting udev
Creating root device
Mounting root filesystem
EXT2-fs: magic mismatch, very weird!
Mount: error 22 mounting EXT2
Mount: error 2 mounting none
Switching to the new root
Switchroot: mount failed: 22
mount /initrd/dev failed: 2
Kernel panic - not syncing: Attempted to kill init!

<END OF FIRST IMAGE MESSAGE>

<SECOND RUNNED IMAGE>

Redhat nash version 4.2.1.8 starting
Mounted /proc filesystem
Mounting sysfs
Creating /dev
Starting udev
Creating root device
Mounting root filesystem
VFS: couldn't find ext2 filesystem on dev hda1
Mount: error 22 mounting EXT2
Mount: error 2 mounting none
Switching to the new root
Switchroot: mount failed: 22
mount /initrd/dev failed: 2
Kernel panic - not syncing: Attempted to kill init!

<END OF SECOND IMAGE MESSAGES>