Can't copy & paste text or move files in MacOS Sierra

I am using a MacBook Pro (Retina, 15-inch, Late 2013). I recently upgraded to MacOS Sierra (10.12.1). I can no longer copy and paste text between files or applications. I also cannot move files in the finder. Logging out or restarting fixes the problems, but only temporarily. Restarting with Safe Restart also fixes the problems, but they return when I then restart normally. Has anyone found a solution for these problems?