hey i had the same problem with my computer. i have a sony vaio, and i have the realtek driver
i found its a problem with vista. the updates stuff it up
fixed mine by downloading the driver again from the sony website and then uninstalling the driver currently on my computer, then reinstalling the one from the site. i also changed the windows update from automatic to 'ask me first'
I suppose everytime i d/l a new service pack ill probably have to do this, unless the vista people fix this up
hope this works for you aswell