I had similar issues. I went to CMD prompt and did a winsock reset, and it corrected my issues for temporarily. I also had a wireless connection, that would constantly go local. I moved the computer closer to my router and went copper. Now, when I am on the network, some applications such as ZUNE says I am not online. IE sometimes also tells me I am offline, retry or stay offline. I say retry and it opens my web page. I finally completely removed my wireless card, and again did a winsock reset and still had issues. I ended up reloading VISTA and in the process found a vista driver for my VIA GigabitEthernet controller and so far, it looks like things are working ok, though it could just be that re-installing the driver did it. Vista Networking has some bugs me thinks.