i hold these packages to squeeze versions:
live-boot
live-boot-initramfs-tools
live-config
live-config-sysvinit
this worked for me in october but some change in unstable after that time caused
the live boot to fail with error:
/init: line 7: /lib/udev/path_id: not found
after much work i have solved the problem.
udev package must have been the change, or something relating to it.
i found that you MUST use the corresponding version of live-boot-initramfs-tools
i suggest you use versions of udev and live-boot-initramfs-tools from the same
dist.
if you continue to fail then check version differences between testing and
unstable, likely you need live-boot-initramfs-tools pulled from unstable.