You might want to try the first software release that includes drivers for Windows Server 2012 at http://downloadcenter.intel.com/Detail_Desc.aspx?DwnldID=21642. (These drivers weren't here last week when you first posted.) Just ignore that the OS says Windows 8 instead of Windows Server 2012. The OS hasn't been added to the list yet. That addition is coming soon.
If you do try out the new drivers, let me know if that fixes your issue.