I found this http://blogs.southworks.net/aalvarez/2008/11/15/hyper-v-server-first-steps-and-troubleshooting/ after a quick google.
The Intel patch you got before - was it a patch for the board, the NIC, or what? There might be something similar coming if it's not one of the older components.
Thanks for your answer!
The patch I was using with Server 2008 was this one: http://downloadcenter.intel.com/Detail_Desc.aspx?agr=Y&DwnldID=17188
But that isn't working for Server 2008 R2.