One moment my system was fine. I tried to use Skype and could not get microphone to work. I tried starting pulseaudio volume control. It would not start. After reboots and a lot of messing about I removed and reinstalled pulseaudio. Then when I rebooted there was no desktop. A right click gave me options including terminal and web-browser (I think this is openbox). I tried 'startlxde' from terminal and was told it was not installed. I did:
sudo apt-get install --reinstall lxdm lubuntu-desktop
now if I type startlxde in a terminal I get a desktop, albeit completely unlike my old one. However it does not start automatically. How can I fix this ?
Also the microphone now works fine, but there is no output sound. Should I just salvage any personal work and start to install everything from scratch ?
To get the Lubuntu desktop back, I right-clicked in the black openbox desktop and selected logout. This brought up the greeter screen that I was familiar with. I had never noticed the buttons in the top right corner before (never needed to use them). One of these is a pull-down which allows me to select the desktop environment. Openbox was selected. I changed the selection to Lubuntu Desktop and logged in as normal. This gave me the desktop I am used to with all my taskbar customisations intact.
The good thing is that the desktop selection is rememembered. Subsequent reboots took me straight to Lubuntu desktop instead of Openbox.