It used to work on 3.0 (maybe by luck :D)
So you are using 3.1 and it works fine in the 3.0 ?
Besides it maybe some bug on the 3.1 what is must possible ( I could not use 3.1 yet for any of my games, too many bugs ), I would try to clean the camera as well and see what happens…
I had problems with cameras when using this type of custom rendering, the camera is part of the rendering, so you need to take care of it: [SOLVED] Cant move the camera when rendering to texture - #12 by wagfeliz