Well done
The command you typed in was to stop what is called "Receive Window Auto-Tuning" where Vista is constantly changing the amount of data that can be received depending on Network conditions.
Apparently not all routers..etc can handle this can cannot get the data to you correctly.
From Microsoft:
"Note Some Internet gateway devices and firewalls block packet flows because they do not correctly interpret the scaling factor used in TCP connections. Because of this, Internet Explorer in Windows Vista uses an initial scaling factor of 2. Other applications use a default initial scaling factor of 8. Microsoft is investigating changing the initial scaling factor for Internet Explorer-based connections to 8 in a future update of Windows Vista. Microsoft is working with the manufacturers of these devices so that they can be updated for compliance with TCP window scaling."
Well done again. I hope this can help other people in the same postition as you.
Steve