Hi Lars,
For debugging you could set BUSYBOX=yes and DELAY=5 in /etc/mkinitrd/mkinitrd.conf and rebuild the initrd. At boot time you will be prompted to enter a tiny shell.
Using 'cat /proc/modules' in this shell session you should verify that the driver for the root filesystem has been loaded. If it is missing, then it should be added to the modules file, too. You can even try to manually mount the root filesystem and check the error message. (Please umount it again before you press the reset button. The tiny shell seems to be a dead end street.)
Another reason for your problem might be that the sequence of found disks has changed somehow for your PC, e.g. /dev/sda has become /dev/sdb.
Good luck
Harri
