Please see the code below-These are the profile attributes we are trying to update and we are getting above error.when it calls the upsert,it throws the error-

userFields[1] = makeElement("Alias", u.firstName.Substring(0, 1) + lastName);
userFields[2] = makeElement("CompanyName", u.companyName);
userFields[3] = makeElement("Department", u.department);
userFields[4] = makeElement("Division", u.division);
userFields[5] = makeElement("Email", u.email);
userFields[6] = makeElement("EmailEncodingKey", u.emailEncodingKey);
userFields[7] = makeElement("EmployeeNumber", u.employeeNumber);
userFields[8] = makeElement("Fax", u.fax);
userFields[9] = makeElement("FederationIdentifier", u.federationIdentifier);
userFields[10] = makeElement("FirstName", u.firstName);
userFields[11] = makeElement("LanguageLocaleKey", u.languageLocaleKey);
userFields[12] = makeElement("LastName", u.lastName);
userFields[13] = makeElement("LocaleSidKey", u.localeSidKey);
userFields[14] = makeElement("MobilePhone", u.mobilePhone);
userFields[15] = makeElement("CommunityNickname", u.firstName.Substring(0, 1) + "_" + u.lastName);
userFields[16] = makeElement("Phone", u.phone);
userFields[17] = makeElement("TimeZoneSidKey", "America/Chicago");
userFields[18] = makeElement("Username", u.email);
userFields[19] = makeElement("EmployeeNumber__c", u.employeeNumber);
userFields[20] = makeElement("Title", u.title);
userFields[21] = makeElement("ProfileId", "xyz");
userFields[22] = makeElement("ManagerId", u.manager);
newUser.type = "User";
newUser.Any = userFields;
userList[x] = newUser;
UpsertResult[] results = binding.upsert("EmployeeNumber__c", userList);
for (int j = 0; j < results.Length; j++)
{
if (j == x)
{
if (results[j].success)
{
successes++;
else
{
errors++;
for (int i = 0; i < results[j].errors.Length; i++)
{
Error err = results[j].errors[i];
Console.WriteLine("Errors were found on item " + j.ToString());
Console.WriteLine("Error code is: " + err.statusCode.ToString());
Console.WriteLine("Error message: " + err.message);
}
}
}
}

Also, I am trying to use upsert to update a record and i get this message for some records-"Duplicate Username.<br>The username already exists in this or another Salesforce organization. Usernames must be unique across all Salesforce organizations. To resolve, use a different username (it doesn't need to match the user's email address). ".
It works for certain users but not all?The empoyee number, email address match but i get this exception.

Another thing is when i try to insert new user, i get an error asking to "Business unit must be defined by user".I am already passing company name,division,district etc.


I am trying to update the profile information.So, even if username exists, it should have updated the record right when i use Upsert.Why is it trying to insert and giving me "Duplicate Username.<br>The username already exists in this or another Salesforce organization. Usernames must be unique across all Salesforce organizations. To resolve, use a different username (it doesn't need to match the user's email address). ".Is it looking at UserName field only or is it looking at any other fields to determine whether it is a insert or update?Is it not supposed to insert when username does not exist and update when username exists?