Yes, I have seen similar errors too. Some systems seem to be unable to recognize the cramfs format on their own. You can try to mount manually:

Code:
su
mkdir /mnt/test
mount my.cmg /mnt/test -o loop -t cramfs
/mnt/test/wrapper
If you get an error about "no free loop device", then you have tried already several times w/o success and need to reboot first.

Greetings,
probono