It's probably my fault, I have 127 recordings of (blush) Antiques Roadshow in a subdirectory.  Whilst scrolling up/down to find the one I want, the screen froze up.


Left it for 1/2 hour (well, at least 10 minutes) then cycled the power to get control.


Booted up fine but the next day noted that the daily download had not completed, with a SO3 error.  Major panic ensued.  Tried another restart, same.  


Then remembered the TiVo kickstarts and checked on WeaKnees site again.


Restarted and ran kickstart 57 file repair and it worked.  So if you have an error, try the kickstart fix.  I regularly run KS54 (disk test) to check hard drives in my herd.