By the way, this is the conclusion of the story.
I had, you recall, somehow lost all the icons in kontact during a new install of Mandriva, and asked the list for help. They were putting up with it until I figured out what to do.
So having got some wisdom here, or at least useful suggestions, I go in to visit last week, and discover it will not boot the default. Not only that, but there seem to be some extra boot options in grub. Who knows, maybe they did an update? Its hard to get a clear account. So I boot from the latest kernel version of the new options, and it starts fine. So just to check, I boot again from the default, and now that boots fine. Very odd. And guess what, all the icons have come back of their own accord!
In another part of the wood, another Mandriva system, after system update it cannot start X. Then, same process as above, it can start X but only in 640 x 480 mode. The solution here turned out to be, use the xorg not the nvidia drivers, and all was fine again.
I know, put them on Debian..... But the thing is, the Mandriva control centre is so easy for people to use. When it works. Oh well.
Al