Either installing or running Calibre does something to one of the packages which the ubuntu desktop depends on. I was able to get it working again with this:
Code:
apt-cache depends ubuntu-desktop | grep Depends | sed 's/ Depends: //' | xargs apt-get --reinstall install -y
Anyhow, I'd like to get a newer calibre working, but I think I'll be a little more careful with installation next time.
-mark