Slowdowns in performance when connecting from Vista to Vista, or Vista to Server 2003 Operating Systems are most likely related to the new Auto-Tuning (throttling) features within the upgraded TCP stack included in Vista and 2003 Server.  Only a few users have reported significant slowdowns in this scenario and disabling auto-tuning resolved the issues.

See the following articles for more information:   

Description of Windows 2000 and Windows Server 2003 TCP Features
http://support.microsoft.com/kb/224829

-or-

http://robgarrett.com/cs/blogs/software/archive/2006/12/31/vista-firefox-2-slow-network.aspx


Note, turning off auto-tuning on the server will not produce undesirable performance.  Until recently, most (if not all) clients connecting to Windows 2003 did so without requesting auto-tuning.  By default, Windows 2003 will not enable auto-tuning unless it is requested by the client - Vista!  Disabling auto-tuning with this registry change will assume XP-like behavior.

The primary issue appears to be with the addition of Vista's "Receive Window Auto-Tuning Level" setting in the TCP/IP stack.  Disabling this setting fixed the timeout problem in FF2 and Windows Live Writer on test machines. 

When running as an Administrator, open a command window and execute the following command at the prompt:

netsh interface tcp set global autotuning=disabled

Changing "disabled" to "normal" will re-enable this setting if so desired.  The following command will list the status of the current TCP settings:

netsh interface tcp show global