I had the same problem and I found out it was a problem with the vista drivers for my gigabit network card. If you're having these problems and you have a Marvel Yukon Gigabit ethernet controller you need to download the drivers directly from the Marvell site as the drivers vista installs don't work.

just go here:
Marvell: Consumer Driver Search

and run a search based on the platform you're using. should solve your problems if you have a gigabit ethernet controller

Let me know how it goes