I found the risk: it is not stable, I have to set on IIS Anonymous access Disabled and Windows access Enabled. Then setup the GetTicket.
Problem now is to make work GetTicket with Workbench in cross domain. It seems to have multi-hop authentication.
I can see in debug, that I get the ticket correctly, but I get the "Qv is undefined error". But I managed to make it work bu using the QProxy.aspx, and modifying it forcing authentication by replacing default credentials with the credential of an QlikView Administrator member(that is in another domain) :
NetworkCredential networkCredential = new NetworkCredential(user, pwd);
// Associate the 'NetworkCredential' object with the 'WebRequest' object.
request.Credentials = networkCredential;
//request.UseDefaultCredentials = true;
//request.Credentials = CredentialCache.DefaultCredentials;
request.KeepAlive = false;