Unity3d: calling a web service in unity editor works, but not in standalone. Why?

Unity3d: calling a web service in unity editor works, but not in standalone. Why?

I have this line of code: 
   SDE3D _webService = new SDE3D();
   int result = _webService.UserLogin(txtLoginUsername.text, hashString);

My UserLogin function looks like this:
[System.Web.Services.Protocols.SoapDocumentMethodAttribute("http://www.something.com/UserLogin", RequestNamespace="http://www.something.com/", ResponseNamespace="http://www.something.com/", Use=System.Web.Services.Description.SoapBindingUse.Literal, ParameterStyle=System.Web.Services.Protocols.SoapParameterStyle.Wrapped)]
public int UserLogin(string username, string password) {
    object[] results = this.Invoke("UserLogin", new object[] {
                username,
                password});
    return ((int)(results[0]));
}

In the Unity Editor it works well.
At runtime, in my Unity game build, it doesn't work and doesn't return any error message!
What is the issue?
Thanks

Solutions/Answers:

References