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