the error you are getting is a CSS Form Builder 2 error.
Did you install version 2, then uninstall it and install version 1?
If you install version 2, you should uninstall HTML Editor and Universal Email. Those extensions are included in CSS Form Builder Version 2.
Did you install form builder 1 over form builder 2? what was your sequence?
When installing a new extension, you should always uninstall the other version first.