Word 2010 - Comboboxes do not change their visual item focus

The combo boxes in Word 2010 (at least...) do not change their visual item focus when one hoovers (or uses the keyboard up-down arrow keys) nor do not scroll to put the selected item onto screen. They however capture mouse events.
It may be due to a problem related to how some events are sent to windows (here, the list box associated to the combobox) whose parent window has been changed...
See attached screenshot: the expected behaviour in this example would be that the font "Goudy Old Style" is selected in the font combobox, the "Bold" ("Gras" in fr) is selected in the style combobox (instead of "medium"), and that point size "12" be selected.