I have a Galaxy SIII ATT USA.
I rooted and flashed CM10 serveral months ago. It has been great. Then I got an update message, so I let it.
This apparently took me to jelly bean 4.2.2(? it had the lock screen widgets for camera and stuff so that why I think it was 4.2.2) However, everything was messed up. google account was missing, bacground changed. several app crash notes on boot... you get the idea.
I tried to restore a backup but RomManager would crash. I went back to stock and tried to start over.
I got the stock rooted with odin, then updated in Rommanager but when I tried to load CM 10 I got stuck at the cyanogenmod loading screen. It just stayed there spinning. I pulled the battery and and powered on, same issue. So I restored from clockwork to my rooted stock.