Hi!
On my computer there are 2 NVS 810 video cards with a total of 16 outputs. However, the Arena Resolum sees only 8 outputs. How to fix this problem. It is present in both Windows and Mac OS X.
Do you have 16 actual outputs connected to your 2 NVS 810 cards?
Also, you mention in your first post that you see the 16 outputs on Mac OS X, do you have your 2 NVS 810 cards on a Mac Pro or are you using a Hackintosh?