Commented Unassigned: Error registering task on Windows Vista [12469]

On Windows Vista, I can't register a task when a password is required. I'm using the version 2.5.27 of the wrapper.
The next code works on other operative systems, but not in Windows Vista:

TaskDefinition td = taskScheduler.NewTask();
td.Actions.Add(Application.ExecutablePath, string.Format("\"{0}\"", configPath));
td.Settings.DisallowStartIfOnBatteries = false;
td.Settings.StopIfGoingOnBatteries = false;

Task task = taskScheduler.RootFolder.RegisterTaskDefinition(taskName, td);
task.Definition.Principal.LogonType = TaskLogonType.Password;
task.Definition.Principal.RunLevel = TaskRunLevel.Highest;

TaskEditDialog editorForm = new TaskEditDialog(task, true, true);
editorForm.ShowDialog();

When clicking on OK button of the Task Edit Dialog, we are prompted to type password of the account. Even if the password is right, we get the error of the screenshot.
Comments: ** Comment from web user: dahall **

I'm struggling to find the error in the code that would cause this problem only on Vista. My last thought is to ask you to tell me what you see for the "user" in the password prompt. I'm curious if I'm not getting the full user name to pass to the Register method.