I put in my wireless mouse while Alt+Tab. Weirdly the game's menu sliders then vanished! An odd bug for sure, but figured I'd report it anyway.
EDIT: Oh yeah, I should probably add some more details. Duh >< Clicking around where the sliders were produces no reaction at all. Closing and reopening the menu doesn't help. This is both on the music and graphics screens. Restarting solves issue.