[Seaside] WAComponentsNotFoundError when working the To Do tutorial from "An Introduction to Seaside"

[Steven Greenberg]

Hi.  I'm getting an error, and I'm not sure what to do.  I've
completed the exercises up through chapter 4.  I get the list of
tasks, and the menu bar across the top.  The problem is that, when I
click one of the links, I get "WAComponentsNotFoundError".

The system suggests these possible causes:

    * you do not implement #children correctly
    * you do not backtrack #children correctly
    * you do not implement #states correctly

I put a breakpoint in #children, and it appears to be returning the
right components.

Do I need to explicitly turn on backtracking?  I'm not familiar with
#states, was I supposed to do something with that?

I'm working with the "Developer Image" from seaside.st.  Squeak 3.9,
Seaside 2.8a1.  I did not use monticello or update any of the
packages.

Any suggestions?

    Thanks,
    Steve