I'm using Xubuntu 11.04. Before everything worked fine, but when booting today the following happened:

1) Window focus does not leave the first-opened program. This means that if I keep Firefox open, and open a terminal, window focus will never be transferred to the terminal.

(EDIT: if I open a terminal first, and then open Firefox, Firefox steals focus)

2) Window menus have disappeared. The maximize, minimize, etc., buttons and menu are gone.

3) In Xfce Settings Manager, the "Window Manager" settings window is empty. There is just a gray screen there, so I cannot modify any window settings.

4) The keyboard shortcuts I had previously defined using the Settings Manager do no longer work. Further, ALT-TAB no longer works for cycling between windows.

5) The mouse pointer does not show when I first log in. I have to log out and log in again (with an invisible pointer) before the mouse shows itself.

EDIT: 6) I cannot resize or move the Thunderbird window, but I can move the Firefox window

What can I do to troubleshoot this?