Different versions of Rhino running on the same computer may have caused problems because they were sharing and overwriting each other’s rhinoscriptsyntax python library. The files are now hosted directly in the application bundle. A few versions ago we also upgraded the Python standard lib to version 2.7.5 and it is also in the application bundle.
An easy way to see where these files are now located is to upgrade to the latest version of the Atom rhino-python package and press the alt + cmd + s keys (after running the StartAtomEditorListener command in Rhino) to launch the search paths dialog box. See also the Manage Python Search Paths section of the updated docs.
Hope this helps and we look forward to your feedback,
Alain