Hi Ian,
I had a similar problem some time ago. It got worse and worse. After some time
the guru even occured when executing a simple LIST-command. After booting the
machine from floppy, the problem was gone.
Because I suspected a hardware-problem with the HD I went to my Amiga-shop.
They tried some combinations of controllers & HD. After all this, the data on
the HD itself was blamed (virus?) and they took the liberty of formatting the
HD (needless to say I did'nt have a backup). I never had that error again (1
year ago).
I don't know if you are having the same problem I had, but try booting from
floppy and see what happens.
Hope this helps,
Karl Van Hoyweghen (going offline a few days
for rebuilding my A4000 in Z7-tower)