I hope someone from the ATI driver developers will read this:
The following call to glBlitFramebuffer…
glBlitFramebufferEXT(0, 0, Width, Height, 0, 0, Width, Height, GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT, GL_NEAREST);
…does not copy the depth values if the depth buffer has
the format GL_DEPTH24_STENCIL8_EXT, the source buffer is
multisampled and the destination buffer is singlesampled.
A workaround is to call glBlitFramebufferEXT without the
GL_STENCIL_BUFFER_BIT although a packed depth stencil
renderbuffer is used (GL_DEPTH24_STENCIL8_EXT).
Here is a full description.
This issue is only reproduceable on ATI Radeon HD 5850
with latest driver. I was not able to reproduce it on
ATI Mobility Radeon HD 3400 or NVidia 8800 GTS.