You can boot into single user mode.
With Lilo, you can select the OS from the menu and add a 1 to the end.
Eg.
boot: Linux 1
Edit /etc/fstab
/dev/hda3 /data reiserfs noauto
The noauto option will not try to mount the filesystem on reboot.
Reboot to multi-user mode and you can try to recover the filesystem.
"If you always do what you've always done, you will always be where you've always been."