Boy do I feel dumb now.
My bud and I tried redoing the turn from a phase or two previous. That worked, even though I had to wait about 45 seconds after the 60 seconds was displayed. Cool, I thought, but then I got to wondering if I'd waited long enough on the turn I was complaining about. Ran it, and it displayed the DONE button 90 seconds after it showed 60 seconds. I don't know what the damn thing is thinking, but impatience is clearly a vice in this business. The scenario is pretty large (1.3 Meg on this particular phase), and my machine is pretty dated (P2-233, 256M Ram, 32M video card), so maybe the old girl is just bogging down a bit much?
Thanks for the consideration,
Poilu