Try editing in a new project with new data as a test.
If that doesn't work then there may be something with your installation or your profile.
You can do a "repair" from windows control panel's Add/Remove programs to see if that fixes issues
Reset your application profile if that doesn't work.
If none of the above works your upgrade didn't go smoothly and a complete deinstall removing all artifacts of any arc* products or other products that it uses may be needed