do you also have problems with glBlitFramebufferEXT() and
Multisampling on ATI cards?
Using glBlitFramebufferEXT() to blit a multisampled color
renderbuffer from a FBO directly to the main window buffer
does not work. But it should work according to the spec.
And it works with NVidia graphic cards. A workaround on ATI
cards is to downsample the multisampled color buffer to a
singlesampled buffer and then blit the singlesampled buffer
to the main window.