Peter, Corey and I tore apart my T-case last night, and found the front output shaft was pushed forward out of the T-case enough that the front drive wasn't engaging. It seems that there was a large snap-ring that was omitted in the rebuild last summer, and that allowed things to walk forward. I'm sure my stress-test of the t-case with trying to run different gears a couple weeks before the event didn't help either.