After update to Jaunty - no desktop

[fululian]

After i did the update from 8.10 to 9.04 last night, and while getting everythin else to work, my desktop has disappeared. panels, menus and everything else is there, but as a desktop, there is only the wallpaper - no icons, drives, and no right-click with the mouse. also, i can't switch users, if i do, it tells me that "authentification has failed", and i have to pull the plug and reboot.

the package "gnome-desktop-environment" wasn't installed, but with it on board, the situation hasn't changed.

So what should i do?

Thanks