Activity import gives "no matching contact" error when matching on Email

I am attempting to import a CSV file of about 300 activities on CiviCRM 4.1.3, sitting on Drupal 7.14. The field I am matching on is email address. The error given is: No matching Contact found for (EMAIL ADDRESS )

Note the whitespace before the closed parenthesis. This space doesn't exist in my file, unless the carriage return between records is somehow being treated as whitespace.