Connecting to a web service that using Integrated Windows security

[TheNortonZ]

I have a web service that will be used internally to our company that is
setup for integrated security. I connect to it on my local machine like
this:

WeatherClient.localhost.WeatherService svc = new
Weatherclient.localhost.WeatherService();

svc.Credentials = System.Net.CredentialCache.DefaultCredentials;

WeatherData info = svc.GetWeather(this.CityTextBox.ToString());

If I have both the client and web service on my machine, no problems, but
when the client is on a different machine I get this error:

HTTP status 407: Proxy Authentication Required ( The ISA Server requires
authorization to fulfill the request. Access to the Web Proxy service is
denied.

I have even gone as far as setting myself up as an administrator on the web
service machine just to see if it makes a difference. Could this be a
problem with the ASPNet account?

Thanks.

Norton