Vista SP1 Machines drop Internet connection (LAN still Acessable)

I'm currently experiecing a wiered issue with Vista machines.
Below is my company's current situation:

We were infected with w32.downadup.b and as part of the removal
process we upgraded all of our machines with the latest patches, we
took each machine off the network and cleaned them manually one at a
time. Our network consists of VISTA and XP workstations and Win 2K &
2K3 servers. (Win2k DC)

Once it was determined that all machines were clean we turned on the
network. It was then we noticed the drops on all VISTA SP1 machines.

The following symptoms occur:

Vista randomly (it seems) drops Internet connection during which:
- LAN access is available
- Able to ping local computers including DC
- Able to perform nslookup (Primary DNS is DC)
- Able to perform reverse-nslookup
- UNABLE to ping websites (google / cnn / bbc)
- UNABLE to ping websites via IP address
- UNABLE to browse the internet via Chrome / Explorer / Safari

It's very odd and we've been unable to find a solution. There are
about 30+ VISTA machines (laptops and desktops).
Any help is greatly appreciated!

Farhan <> wrote:
>
> I'm currently experiecing a wiered issue with Vista machines.
> Below is my company's current situation:
>
> We were infected with w32.downadup.b and as part of the removal
> process we upgraded all of our machines with the latest patches, we
> took each machine off the network and cleaned them manually one at a
> time. Our network consists of VISTA and XP workstations and Win 2K &
> 2K3 servers. (Win2k DC)
>
> Once it was determined that all machines were clean we turned on the
> network. It was then we noticed the drops on all VISTA SP1 machines.
>
> The following symptoms occur:
>
> Vista randomly (it seems) drops Internet connection during which:
> - LAN access is available
> - Able to ping local computers including DC
> - Able to perform nslookup (Primary DNS is DC)
> - Able to perform reverse-nslookup
> - UNABLE to ping websites (google / cnn / bbc)
> - UNABLE to ping websites via IP address
> - UNABLE to browse the internet via Chrome / Explorer / Safari
>
> It's very odd and we've been unable to find a solution. There are
> about 30+ VISTA machines (laptops and desktops).
> Any help is greatly appreciated!

Have you tried resetting the Winsock settings?

netsh winsock reset

What about the TCP/IP stack?

netsh int ip reset c:\tcpresetlog.txt

ss.