How do I save the Import/Export CSV with Excel on Mac OS X?
If you're using Excel on Mac OS X to open and edit the export CSV file generated by s2Member, you'll want to make sure that you save your changes in the Format of "Windows Comma Separated (.csv)":
If you save it as a regular CSV file inside Excel on Mac OS X, you may have trouble importing the CSV file into s2Member. This is because Excel on Mac OS X adds old type of line ending that may be incompatible with the PHP configuration on your server. See Issue #597 for the technical details.