CS6/Decklink Lag on Mac

Hi all, wondering if anyone can help.

My setup:

Mac Pro 5,1 (2x Quad Core 2.4Ghz)
26GB RAM
ATI Radeon HD 5770
BMD Decklink Extreme HD 3D
JVC HD Reference Monitor
2x Desktop Monitors
Premiere Pro CS6

I've installed the latest Desktop Video Drivers etc, and am getting playback on sequences using the JVC, however it is a few frames out (late), which makes it unusable for promo/general cutting.

This is a real shame, as I haven't been able to use it at all properly on any build of CS yet for various reasons/bugs.

Can anyone help? I can see a reference output timing option in Sys Pref, but it seems to have no effect?

Thanks in advance

Dan