newbie - menu disappears

[Gilgam Webdesign et conseil]

+ My desktop or desktop menu has disappeared!?

It appears that xfdesktop is no longer in control of the desktop. Often
xfdesktop has died, or some other program took over the desktop. Make
sure that xfdesktop is still running first. Nautilus takes over the
desktop by default too. Please start nautilus with the --no-desktop
flag, or use gconf-editor and unset the flag that tells nautilus to
handle the desktop (/apps/nautilus/preferences/show_desktop). Start
xfdesktop again and you should be OK again.

Hi i've installed xubuntu on a computer illiterate user, and he is  
satisfied with, but in changing the desktop background, the menu  
disappeared from the right click and in the panel .

i've seen the explanination above but do you have something with more  
explainations  (what should i type in console...) ?


Thanks

Nicolas gruson