Yes, and the easiest way is to install them via command line in the Terminal

sudo aptitude update
sudo aptitude install xubuntu-desktop
sudo aptitude install lxde
sudo aptitude install fvwm-crystal

or whichever you want. All of them are quite OK

I myself think this blackening or "grey-out" is an isolated case but it
happened to me in Gutsy Gibbon (rarely), in Hardy Heron (sometimes) and
in the present Ubuntu 10.04 rather often.