Hi Greg,
Unfortunatly I am having some major problems with my PC and so have stopped all Moodle work for the time being.
The only thing I can suggest at the moment so that you can progress with marking and such is to enable Allow theme change in URL which is found in:
Administration > Site Administration > Appearance > Themes > Themes settings
This way you can use the Clean theme when needing to access the Gradebook, by adding the following after your sites URL in the browsers address bar:
?theme=clean
Unless of course someone else may be able to suggest a fix for the Magazine theme.
Hope this helps?
Mary