So you can´t set tcp autotuning to disabled after vista sp2?

Exactly this was my problem today morning. No one in the newsgroups seemed to have a solution. Now what I did was start a netsh shell and looked around for this "heuristics" feature which was obviously introduced with sp2. Finally, I found out you have to disable this heuristic first before you can set autotuning to disabled. The steps are: 

netsh

interface

tcp

set heuristics disabled

set global autotuninglevel=disabled

and...here you go.