We have an internal telephone system managment website that has work perfectlyt up until SP1. The website uses Multicast and Unicast for networking. Heres the strange part, the site does not work when connected to the local lan but if I use our VPN it works.. I have been using IE9 Did MS make any changes to network in SP1? Shawn

Hi Shawn, For the details in service pack 1, please download the doc from: http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=269 Have you tried Compatibility View in IE9? As I test, on one Windows 7, uninstall the sp1, how's the result? If it takes long time, you can also use the Network Monitor to capture the network traffic, this could help you find the failed steps. Regards, MiyaThis posting is provided "AS IS" with no warranties, and confers no rights. | Please remember to click "Mark as Answer" on the post that helps you, and to click "Unmark as Answer" if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.