Try calling:
-- Bind each buffer to a face of the cubemap
SetColorBuffer(cubemapbufferpx, cubemap, 0, 0) -- positive x
SetColorBuffer(cubemapbuffernx, cubemap, 0, 1) -- negative x
SetColorBuffer(cubemapbufferpy, cubemap, 0, 2) -- positive y
SetColorBuffer(cubemapbufferny, cubemap, 0, 3) -- negative y
SetColorBuffer(cubemapbufferpz, cubemap, 0, 4) -- positive z
SetColorBuffer(cubemapbuffernz, cubemap, 0, 5) -- negative z
after every render.