Bug#433127: system unbootable after update to linux-image-2.6.21-2

[Stefan Schöttke <schoeddie@gmx.net>]

package: linux-image-2.6-686
version: 2.6.21-2
severity: grave

Hello,
after upgrading to the current kernel package (2.6.21-2) the 
boot-process failed, reporting that the system was unable to find 
/dev/hda1. Then a shell (busybox) was started. The older 2.6.18-4 kernel 
works without any problems.
The reported message was:
ALERT! /dev/hda1 does not exist. Dropping to a shell!
      Check your root= boot argument (cat /proc/cmdline)
Check for missing modules (cat /proc/modules), or device files (ls /dev)
BusyBox v1.1.3 (Debian 1:1.1.3-4) Built-in shell (ash)
Enter 'help' for a list of built-in commands.
/bin/sh: can't access tty; job control turned off (initramfs)

Greetings,
Stefan