The same thing happened to me when I upgraded to Graphene 1.9.2
This was not a clean upgrade for me since it was missing a key css file.
I downloaded the graphene.1.9.2.zip file and replaced the entire contents of my wp_content/themes/graphene directory which got the theme working but the visual editor still did not work. As above it works fine when I activate other themes.
Other stuff must have been missing or corrupted as well.
