He was absolutely right – it was an Intel / xorg driver issue causing the lockups.
A big shout out to doniphon for updating and testing Xorg at the 20⁄20 Conference last week. I’m running the latest Xorg on my T61, and the lock-ups are gone!
And I’m still loving the T61. Great Linux support, good form factor, and a great value. All I have left to do is figure out a bug with suspend.