Hi Jeff, Thanks for getting back to me. Yes, I had been using Labtool in that way, and has also tired using emagin's 3D launcher.
We've actually "solved" the problem by swapping my Quadro FX1800 with a Quadro FX3450 from another machine and it's all working fine. The FX3450 is compatible with earlier NVIDIA drivers which seem to support field sequential stereo and are compatible with the z800 shutter glasses.
Thanks very much for your help. If anyone can offer a fix for getting this to work with the FX1800/ newer driver that would be great....currently it's a bit of a waste of a £500 graphics card
Thank you.