Mac text interpretation (delimiters linefeed/carriage return) is different from Windows, I have had trouble in the past with text files going from one platform to the other. Maybe that’s part of the problem, haven’t got time this morning to test further.
As bigjimslade reported there is a problem when loading point files on Mac, the first point is ignored.
Minimal example:
Import a file with the following points:
0 0 0
0 1 0
1 0 0
1 1 0
You should get 4 points, but Rhino only load 3.