stencil shadows problem

does anyone have an idea what could cause that 3dgs stencil shadows dont work here anymore, but other stencil shadow demos do? since i got a new gpu i am not 100% sure that it could be the gpu is partially defect, but in that case no stencil shadows would work, or is that wrong..
btw, it is the same gpu as before where it worked, a geforce go 6800 ultra,

any ideas? it is really strange