Shutting down gives me a console that repeats 'ext3 journal aborting' ad infinitum. Eventually I just powered it off.

I assume dmesg and /var/log/messages provide no clues? Can you turn off journalling? Perhaps you could try booting from a rescue floppy/CD and mount the drive and see if you get the errors still.

*realises that someday it will probably happen to him*