Two questions:
One: Do you use PPPoE to connect with your cable modem, or is it a static IP? If it's PPPoE you have to change what's called your MTU setting to 1492. Standard MTU setting is 1500 (bytes), but with PPPoE, it has what's called a "header" that's 8 bytes. This can cause slower speeds, and you'll definitely see this on large downloads.
Two: Did you do any patches yet? If not, go to
www.speedguide.com and download their speed patches if you're running Windows.
Any questions/problems, let me know or PM me!