I haven't been able to find out what the T. rex was buried in,
"The specimen was incorporated within a soft, well-sorted sandstone that was interpreted as estuarine in origin." - so it was at a river mouth. And the tyrannosaur was in the Hell Creek, which has been dated seven ways from Sunday as being ~65 million years old.
Science 25 March 2005: Vol. 307. no. 5717, pp. 1952 - 1955, and it's free at sciencemag.org
There's nothing wrong with the dating, Sleve, just with our current understanding of collagen preservation. As I mentioned upthread, perhaps there's an interaction between the minerals of the fossilizing bone and the protein that stabilizes bits of the latter.
The newer Schweitzer study took rather extraordinary care to avoid contamination and to replicate findings. I'm a chemist, not a palaeontologist, but I sure can't see any holes in their methodology. You can bet that a dozen bright young grad students scattered around the world are on the trail of how the preservation occurs.