Thanks guys, but I'm feeling rather embarassed (very sad)
A little bit of RTFLing shows this is a common problem with Gnome 2.8.x - so I should have held of asking.
I think what Microsoft would call a "feature" (laughs).
Well, I am a newbie
A few people have fixed it with a reinstall, but I'm going to try an upgrade to Gnome 2.10 which should make everything OK.