I'm having the same issue with my new (still sitting on MB box for start of build) Extreem4 MB.
RoadRunner Cable. 10 meg down account.
I'm on a 10 meg down connection and get 11 to 11.5 with same cable on another computer.
Unplugged the cable and plunged it into my laptop sitting right next to the MB and get the above download speeds. Plug it back into the MB and goes back down to .82 to 1 down and .02 up.
Anyone find a resolve for this?