Ive had problems myself with the depth stencil format on AMD within the last year or so, so I wouldnt rule that out. Not sure if any of their drivers ever got it right. I was using the depth24 stencil8. Not sure which version of opengl you are targeting, but you might try binding the depth_stencil texture to both the depth attachment and stencil attachment.
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, tex_depthstencil, 0); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_TEXTURE_2D, tex_depthstencil, 0);
Extension ARB_depth_buffer_float provides DEPTH32F_STENCIL which requires extension EXT_packed_depth_stencil, see use example at bottom of page
see if that helps