I haven't seen this before & I'm somewhat confused. The error would indicate that you can't resolve the URL, so maybe a DNS issue upstream from you. But then you said that it works in IE, which means your machine is indeed resolving the URL. Do you have any firewalls turned on on your local PC? Or anything that might be blocking http traffic coming from things other than IE? Not sure.......Could you try pulling some of the Yahoo API call out into a Windows form, and go into debug and watch as you step through?