Batch Create There was an error creating a user

Hi can you tell me why I am getting this message in the log file when I upload new sites

2011-07-28 06:39:39 - User: Admin1 created!
2011-07-28 06:39:39 - Blog: shuree5csoundisolatingearphonescom.xxxxxxx.com/ created!
2011-07-28 06:39:40 - There was an error creating a user

this is the info I am inputting into the csv file
URL
senxxxxxxxx.com
Site name
Senxxxxx
User
admin7
User Password have also tried with the correct password
null
Email
xxxxxxxx+site7@gmail.com
user role
administrator
Thanks Ian