Thanks Helen for the link. I don't know how this corruption occurred.
One day it was running fine on my server, and next thing it stopped
working. I certainly didn't touch the server in any way. I can only
think it was because the hard drive had only a few hundred MBs free.

Anyway, I tried the link you gave me by Paul Beach, and got stuck.

gfix failed, and so I moved to step 6. gbak also failed complaining
that a page was of the wrong type.

So, now I'm on step 10.2. I've edited the get_tables.sql file to
point to my file, but I'm not clear on how I execute this file. I've
never used these command line utilities before, and am not sure what
he is writing about regarding an output file.

Thanks for your patience.

-Graham