Some time ago, about a month or so, we had a problem with our SQL Server 2005 running on Windows 2003. What started happening was that the scheduled jobs were failing due to many connections errors. After some searching I found out that the errors could be caused by the TCP/IP chimney offloading. This gets installed with the ‘Scalable Network Pack’ of Microsoft.
One of the things I tried to fix the problem was disable it but this caused even more trouble.