Does anyone know why I get the following error message when I select the Save All action?

Probably, the file root.fpj (in your project root) is read only or

corrupted.

Check whether the file is read only and make it readable.

Perhaps the root.fpj got corrupted. You can fix that with the following

script: http://www.wvanweelden.eu/product/missing-topics-fixer

Kind regards,

Willam