As stated in the previous post, I upgraded several machines to lenny. These machines are virtualized via xen. After the upgrade none of the installation did boot correctly. They stopped right after

INIT: Entering runlevel: 2
Starting system log daemon....
Starting kernel log daemon....
Starting system message bus: dbus.
Starting OpenBSD Secure Shell server: sshd[ 19.189974] NET: Registered protocol family 10
[ 19.190697] lo: Disabled Privacy Extensions
Not starting internet superserver: no services enabled.
Starting periodic command scheduler: crond.

To fix this problem, you need to boot them into single user mode (add extra="single" to your domU configuration file) and add

hvc0:23:respawn:/sbin/getty 38400 hvc0

to /etc/inittab