Can you go into settings and change your logging level to 'Verbose' then try again. Then check your log at <ProgramData>\SolarWinds\UserImportTool to see if there is anything pertinent to the problem you are seeing that you can post back here.
Probably 4 months too late, but I had the same/similar problem.
The user was created but I could not connect with the domain\name.
When I went to the newly created user in the properties, Account Options and unticked "user must change password at next logon" it worked.
I am having the same issue here. The "password" field in the User Import Tool is populated from the spreadsheet, but the password is not being imported. Additionally, I am importing CannotChangePassword: TRUE and PasswordNeverExpires: TRUE. After the import, the checkboxes in the account properties for these values are checked as they should be. However, I can not connect with the account until I manually re-enter the password. Is there any solution for this?
I used this tool last year to import our users into AD and had no issues. I recently had a new computer and downloaded the latest version and I cannot get the password to be set on the newly created users. Is there a fix for this yet? I enabled the logging and this is the error that I am getting...
2015-08-21 18:02:40,591  ERROR UserImportTool.Logger - System.NullReferenceException: Object reference not set to an instance of an object.
at UserImportTool.MappingManager.IsMappingsIdentical(Mapping mapping)
at UserImportTool.MainWindow.btnMapNext_Click(Object sender, RoutedEventArgs e)
Thanks for any assistance that comes!