I’ve upgraded one of our servers to Windows Server 2008 64bit.  After finishing the install I connected to the server using remote desktop and found the remote desktop session to be super sluggish and painfully slow.  Sitting at the console showed no issues with speed.

After a bit of searching the web I found the following instructions fixed the problem:

(On the Server 2008 machine)
Go to Manage Network Connections, right click on your network connection and click properties, click Configure then click on the advanced tab.
Select “IPv4 Large Send Offload” and change the value to Disable.
After about 20 seconds you can reconnect your remote desktop session and it’s all good.

I don’t recommend doing this on a production server until you know what consequences are involved.
I tend to just do then see what happens but this isn’t always a good idea!  :)