Desktop "environment" have vanished.
Through 9/13 I had been running 12.04 under Parallels on my Mac, and all was OK. In 10/13 I upgraded to Parallels 9.0, then around 11/1 I upgraded MacOS to 10.9 (Mavericks). On 11/16 I booted up Ubuntu for the first time since September. It came up OK, with no errors, but the desktop contained only a few folders and documents, right where I had left them. The strip of applications down the left side was gone, as was the "dock" along the bottom.
I couldn't even shut down cleanly, but forced it through Parallels. So ... What can I do to restore my normal desktop environment?