If using user import module for drupal you could run into problems of delimiters. By default it uses comma and not much better solution which is semicolon, here is a patched filed that has constant on top if you want to change it manually
define ('DELIMITER',';');there are also patches for this to be used automaticly or choosen from admin interface but until this is used in dev or current version, quickest way is to grab file below which is current DEV version edited.