As you may know, Service Pack 2 for Windows Server 2003 included the Scalable Networking Pack (or SNP) which allowed for increased performance in many situations by allowing some TCP functionality to be handled by the network driver and network adapter instead of the Windows TCP/IP stack itself. This functionality was enabled by default in Service Pack 2.
There have been some problems seen in some environments where Windows Server 2003 SP2 has been deployed on systems that support the SNP features. Issues like this have been discussed in several previously published Knowledge Base articles.
There is now a new update available that will turn off the Scalable Networking Pack features on Windows Server 2003 Service Pack 2 systems. The article lists a number of symptoms that have been seen when Windows Server 2003 SNP is enabled and links to download the update for x86, x64, and Itanium-based systems:
An update to turn off default SNP features is available for Windows Server 2003-based and Small Business Server 2003-based computers
Microsoft, Windows Server 2003, SP2, SNP, Scalable Networking Pack