After hours of reading exploratory posts, I found this simple fix for the dreaded "Something has gone wrong" screen:
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Use the Ctl-Alt-F1 key; that should get you back to the Gnome screen.
Then see the info at: http://www.linuxjournal.com/content/res ... ngs-ubuntu
Just some background...
I started by removing MATE from my CentOS 7 system (3.10.0-123), and then trying to install Gnome. It WAS working, I think, but the screensaver came in and the screen went blank. I move the mouse and tapped the ESC key and that probably stopped YUM. There was no title bar, menu or mouse arrow. I rebooted, got a successful log-in as root, and then got the "Oh, no! Something has gone wrong." screen. After hours of reading. I came up with the simple solution above. I got a Gnome GUI screen back, and started an software update. Some 167 packages later, I was back to normal (phew!). That brought the system to 3.10.0-229.4...
Things worked even better when I changed away from classic mode. That let Gnome shell extensions get installed. I don't have the same desktop bells and whistles as with Gnome 2, but that's improving as options come out. And, hey, people listened!