What type of connector are you using to the projector? DVI or HDMI?
thank you for your reply, the projector is connected via HDMI (there is no DVI input unfortunately). i did try a number of different HDMI cables when i first got this problem, and none made any difference.
just to help narrow the problem down a little, i'm pretty sure the PJ is receiving a 120hz signal as it allows "3D mode" to be enabled. any other refresh rate will cause that option to be grayed out.
i can't tell you how long i've been struggling with this problem, and just now i decided to take a look into the hidden settings menu while i was in 3D mode with the nvidia demo up. after a few seconds it switched into 3D! when the hidden menu is up it resets the keystone correction setting, and somehow having it set above 10 had been stopping the 3D effect from working correctly. also kind of explains why i've not heard of anyone else with this problem.
as it's obviously a problem with the projector, i doubt you'll be able to help me further, but thank you for your reply anyway! i hope if anyone else has this issue they have the good fortune to see this thread because i consider myself extremely lucky to have figured this out!