Under Windows 7, the disabled state of the ttk::combobox is not very visible. When disabled, the down arrow is grayed out and there is a slight border change, but the background color of the text area is not changed, nor is the color of the text itself. This makes it difficult to determine the state of the widget at a glance.
Under Windows XP, in addition to the above visual cues, the background color of the text area and the button area are also changed.
The text color is not changed when the widget is disabled under either OS. This does not match the visual look of other disabled ttk widgets (entry, etc), where the text is grayed out also.