(We are still discussing and testing other symptoms that could be related, but if you are having networking issues after the service pack, consider the solution provided on this post. We will update this list as we find more factual information.)
You cannot host Transmission Control Protocol (TCP) connections when
Receive Side Scaling
is enabled, you have Microsoft Windows Server 2003 with Service Pack 2 (SP2) and you use Network Address Translation (NAT) on the server. The TCP connections will be reset.
Update: The following KB explaining the behavior is now public:
You can disable this feature from the advanced properties of the network card under the network interface properties or you can perform the registry changes provided below.
from the TCP/IP stack by doing the following:
Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
To work around this problem, disable Receive Side Scaling when the computer is configured as an Internet Connection Sharing gateway. To do this, follow these steps:
1. Click Start, click Run, type regedit , and then click OK.
2. Locate and then click the following registry subkey:
We have seen several situations where even after completing the steps above, VPN would still not work. On those cases, updating the NIC drivers to the latest version resolved the problem. So, make sure you have the latest version for your Network Card drivers. Most manufacturers have released updated drivers very recently.