Funny, I was looking at this today. It does something odd with the flags, we're not passing back what it expects. In some cases it seems to expect SWAP_COPY to be set, but I added that in and saw no difference, so still a bit of remaining work.
But basically despite the error it's calling DescribePixelFormat not ChoosePixelFormat. We need to find out why it's not happy with the results from that function and fix it.
