Thank you for the update. There may be some problems with some of the 8600GTs not being compliant. The Gigabyte passive model does not say it is HDCP compliant at its web site or at Newegg.
The Gigabyte website only lists the GV-NX86T256D, but the manual lists:
GV-NX86T256H
GV-NX86T256D
GV-NX86T256HP
and notes that only the GV-NX86T256H/GV-NX86T256HP support HDCP. I.e. these two are not actually listed on the website, only in the manual.