Nav. cube won't show with 2D wireframe

At work one of our computers is running Acad 2009. For some reason the nav. cube only shows if I use a visual style other than 2D Wireframe. With the latter it's gone, and seeing how 2D Wireframe is what I use 90% of the time I really miss the cube! I can't find a solution to this in the nav. cube options. Any ideas?

What happens if you enter

-shademode

3d

(just do it)

Is this a viewport in a layout tab or Model space?

What happens if you enter

-shademode

3d

(just do it)

I've gone through all the options, and while the cube does appear with all of them - except 2D - it significantly drags down the performance.

It's the same in both model and paper space.

Mine is somtime there and somtime not in a viewport set to 2d wireframe. I don't really use it though and just haven't bothered to turn off. I would guess it is a bug.