My Oppo BDP-93 comes up and says my display (JVC RS60) is not 3D compatible when I have the Darblet in the loop. I thought this was normal and the Darblet just isnt 3D compatible. When I take it out of the loop 3D works fine. I still use the Darblet daily for 2D with both the plasma and projector, great little device
While I sympathize with your frustrations, I think there is another variable in the equation. If the Darblet is not 3D compatible, then every Darblet owner would be confirming that. But I also have a BDP-93, connected via HDMI to a Denon 4520, then to a Darblet, and finally a Sony display. 3D works fine in this configuration.
I don't have any specific additional trouble-shooting advice--I just want to leave you with some hope that something else might be the root cause.