The GPU hang messages that I had earlier this month are back. They had caused me to restart X, and were thus particularly irritating. But the seemed to come from Google Chrome, so tried shooting it down. Success! Another X session saved. And probably another indication that it's high time to upgrade my system software.
ACM only downloads articles once. It's possible that this article has changed since being downloaded, but the only way you can find out is by looking at the original article.