Just on a wild guess, I launched "Add to Panel" and added the "Indicator Applet" — and a US flag (corresponding to my currently active keyboard layout) showed up in the panel along the top of the screen.
Although (re-)adding the indicator applet seems to have fixed the problem, there is still the question of why the indicator applet became broken in the first place.
Just on a wild guess, I launched "Add to Panel" and added the "Indicator Applet" — and a US flag (corresponding to my currently active keyboard layout) showed up in the panel along the top of the screen.
Although (re-)adding the indicator applet seems to have fixed the problem, there is still the question of why the indicator applet became broken in the first place.