PPC

Ubuntu 5.04 or Debian 3.1 on the original PB G3 (aka Kanga aka PB 3500)

I am trying to get Ubuntu 5.04 or Debian 3.1 running on the original PB G3 (aka Kanga aka 3500). The only problem: the screen is blank after the inital reboot after the installation. Nothing at all (Ubuntu) or only an inverted penguin (Debian). The boot process continues only if one copies over the ramdisk image from the /boot folder onto the HFS partition and specifies it as boot argument. Might it be that the root=/dev/hda8 (in my case the root partition is hda8) is somehow not recognized?