Now i changed the authorization from the Reportserver from Ntlm to Basic...there i can insert my logininformation by aditional headers in den webbrowser.Navigate-method.
But the login-popup still occurs...
byte[] authData = System.Text.UnicodeEncoding.UTF8.GetBytes("user: password");
string authHeader = "Authorization: Basic " + Convert.ToBase64String(authData) + "\r\n";
browser.Navigate(uri, "", null, authHeader);
Any other idears?