visual editing menu not appearing

I’m helping a friend to install a WordPress powered website. The site works perfectly well on my Vista/Chrome installation but on his Windows XP/Explorer machine the icons for the visual and html post/page editing windows don’t appear.

I won’t be able to look at his installation again until tomorrow, but it occurred to me that the version of Flash he’s running may be the problem.

Is that likely? If not, all other thoughts would be very welcome.