I have a copy of David's raw and JPEG files and I'm getting the same results he's been getting so it doesn't seem to be a problem with his DPP or computer set up. It might just be the way DPP "interprets" the raw files coming from his 20D. I went as far as reloading DPP 1.6 (pre picture styles) on my Mac and still got the same results where the raw images is displayed a little brighter than the JPEG. This makes the raw image look blown out even thought it really isn't because highlight details are visible (more so than in the JPEG file).
The current version of DPP, by default, displays David's raw file using the Standard picture style. I had to use the Faithful picture style and then tweak the white point a tad and increast contrast by one notch to get the picture to look like the JPEG image.
I was under the impression that DPP, by default, always renders the raw images very close to what is rendered by the camera in the JPEG format but based on David's raw image, this doesn't seem to be true in all cases, at least not for the raw files from his 20D. I'm now curious to know if this only happens with the 20D cameras or with all cameras (although I haven't personally experienced this with my 30D or 1DmkII).