Changed my power settings so that it would do nothing when I shut the lid on my laptop. Then I had to restart to get the settings to work. After that, when I get to the sign-in screen where I can write my password, after I log on I can only see my wallpaper, no dock or activites bar or anything. I can't even access terminal with superkey + T. I'm running Loki.
This happens to me sometimes as well. I have yet to find the root cause of it or a real fix.
What helps in my case is to press ctrl+alt+F1 to go to a terminal. Log in with your user credentials and type
to (re)start X.
Then, press ctrl+alt+F7 to go back to your desktop.
As a security precaution, I would recommend (if this works) to go back to ctrl+alt+F1 and type
to make sure your user is logged out of this terminal environment.