I am also experiencing this problem. It only happens with effects turned on under System, Preferences, Appearance, Visual Effects. Minimizing or Maximizing the window will wipe away all the corrupted lines, but moving the view or scrolling the cursor will corrupt any text that is new. Sometimes minimizing will fix the problem and it will not re-occur until a new file is opened.
I am also experiencing this problem. It only happens with effects turned on under System, Preferences, Appearance, Visual Effects. Minimizing or Maximizing the window will wipe away all the corrupted lines, but moving the view or scrolling the cursor will corrupt any text that is new. Sometimes minimizing will fix the problem and it will not re-occur until a new file is opened.