Hidden surfaces within Nurbs objects still render in RT

[tricky]

Is there any way to get around this problem?

I have a sub-surface in a nurbs object that is being used to effectively slice another surface. I don't want this 'slicing surface' to be visible to the render. Choosing to hide that surface works for normal rendering, but with RT it is still visible.

(actually, it seems that normal rendering still shows this hidden surface...any ideas?)

[vlado]

Can you post (a part of) the scene?

Best regards,
Vlado