I am the latest stable Ubuntu (10.10) on an Asus netbook and have both GNOME an XFCE installed. I started with Gnome and than installed XFCE because it works slightly faster on that slow computer.
In the beginning everything was fine, but at some point, I don't know when (but it was so also when I was running ubuntu 9.10, before I upgraded to 10), this is what started to happen: when I log in and choose XFCE, I first see my XFCE desktop, then it flickers back and forth between my XFCE and Gnome desktop (but the top panel remains the XFCE one), and eventually it settles on the GNOME desktop (which has its own color, different icons in different positions, and its own context menus).
The general desktop environment is XFCE: the desktop panel and the itmes on it are XFCE, but the desktop area itself is my GNOME desktop.
Any idea why this happens and what I can do to get rid of the display of the GNOME desktop when I choose to use XFCE?