Rendering to a texture..

[Paulius]

You need to initialize the texture with glteximage2d(optionally with data set to nil) before you can call glcopyteximage2d.

He bypases that with glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 0, 0, Width, Height, 0); when creating.
White is what you usually get when texture state is invalid, you sure you're creating it before using? What if you replaced glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, Width, Height); with glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 0, 0, Width, Height, 0);