import contact list into e-newsletter

i am trying to import my .csv file, and when i do it seems to do it incorrectly, it is doubling up on emails in the email and the names columns, and only adding 26 entries at a time... it is very strange. the .csv file has 850 names and emails on it. it is set up with only three columns, email, first name, last name. am i doing something wrong?