Employee Interface - The "User Name" you entered already exists.;The value you provided in User Name

Summary

Error: he "User Name" you entered already exists.;The value you provided in User Name is already used. You must provide a unique value.;

Content

We already have user interface in place. I am trying to setup employee interface using netchange. For the employees, that were already interfaced to Taleo in user interface, I am getting following error

The "User Name" you entered already exists.;The value you provided in User Name is already used. You must provide a unique value.; 

For the employees, who were never part of user interface, employee interface works fine. Any help is appreciated. Please see attached for import definition and temp files.