I just managed to get my Buffalo Linkstation (running Debian based Freelink) to brick in a new way: it would pull the kernel and initrd by tftp over and over again or it would appear to have loaded them but simply stop.
After trawling the forums I have salvaged the situation by mounting the HDD on a linux system and erasing and rebuilding the default /dev/sda1 partition.
I have also recorded how to do it in the relevant wiki article like a good boy:
Linkstations and similar Linux based NAS devices make fantastic home servers - mine draws ~13W under load providing daap, DHCP, NTP, apache, NFS, samba and AFS. Beats the hell out of an always on home Intel server.