Something went wrong with my Xubuntu desktop this morning. Certain things suddenly didn't look right, including the Whisker menu button (equiv. of Start button) showed a generic icon rather than the usual mouse head. So I rebooted, and when it came up it refused to accept my password. I did Ctrl-Alt-F3 and was able to sign in at a command prompt. I tried a number of things, finally running sudo apt reinstall xubuntu-desktop. Now I can sign back into the GUI and everything seems to be working, except networking. The networking icon in the bottom right shows Enable Networking checked. If I uncheck it and recheck it I get the notification "Disconnected - you are now offline" and the networking icon still shows disconnected.
This is a desktop with no WiFi connection; it's on ethernet. The lights on the NIC are blinking, and also on the switch port that the cable's plugged into. I probably just need to reinstall the networking components or something, but don't know how to go about this.
Edit: Hang on, it seems to have repaired itself! Odd.