NFS processes locking up!!

[Zaphod Beeblebrox]

[nfsd's and other processes locking in 'D' state]

One thing I've seen cause this kind of thing is a disk that needs to be
manually fsck'd.  Try bringing up the system in single user and manually
fsck'ing the volume.  I have no idea what causes this kind of state ---
where the disk is bad, but not calling for an fsck.  It could just be random
bad bits, but I've seen this behaviour more than once.