by Guillermo Madero.
Hello Richard,
If it is a recent problem, that means everything was working fine before. So something must have changed (a new component, settings were adjusted, etc.), either at the server or at Moodle itself.
Try and clear the themes cache:
Site Administration > Appearance > Themes > Theme selector, Clear theme caches button.
Also, try and refresh the browser cache (usually by pressing F5).