OK, lastest update:
With trying for hours for making at least one python inside rhino work, I finally found the solution.
I need to delete the folder “IronPython (814d908a-e25c-493d-97e9-ee3861957f49)” in my user folder under c:/User/xxx/app data and reinstall Rhino.
And now both Rhino 5 and Rhino 6 start to work.
I think that folder contains some info that will not update when install/uninstall IronPython or Rhino and causes these error.