LinuxQuestions.org - kernel panic!!! not syncing: not init found

hi,
when i try to pass to kernel the initrd option i get this error:

Code:

Mounting root filesystem

ReiserFS: hda5

...(other ReiserFS stuffs)...

pivotroot: pivot_root(/sysroot,/sysroot/initrd) failed: 2

umount /initrd/proc failed: 2

kernel panic - not syncing: not init found. Try passig init= option to kernel.

grub.conf!

Code:

title=Gentoo Linux (WORKING)

root (hd0,1)

kernel /boot/default root=/dev/hda5



title=Gentoo Linux (NOT WORKING)

root (hd0,1)

kernel /boot/default root=/dev/hda5

initrd=/boot/initrd.img

what's could be wrong with my grub?