I copied the "thematicsamplechildtheme" directory into /wp-content/themes, network-activated it, then went into one of my sites and made "A Thematic Child Theme" the active theme. Upon doing so, widgets disappeared from the public-facing portion of the site, and the "Appearance" menu in the back-end now shows only "Themes" and "Customize"; missing are "Widgets," "Menus" and "Theme Options."
When I make "Thematic" the active theme, all of these problems go away. Completely stumped. Anyone?