I solved the problem by the easiest way - install a lot of xfce4 packages. The command I used was:
Code:
apt-get install `apt-cache search xfce | cut -d ' ' -f1`
I still don't know exactly what the problem was, but I guess that when I uninstalled gnome I also uninstalled some packages I didn't want to or, at least, changed some PATH's.
Thank you again for your help.