Symptom
When opening the Equation Editor, an alert box appears with an error message that says the Symbol font installed is not the correct one.
Solution
1. Quit all open applications.
2. Drag the Symbol font from the Fonts folder to the Trash.
3. Use the AppleWorks installer to perform a custom installation of the Equation Editor (one of the Writing Tools).
This installs a version of the Symbol font that is compatible with AppleWorks.