OK. I put a bread mix in the bread machine this evening so I'd have a freash loaf in the morning. It was a Krusteaz brand Cracked Wheat bread mix. Simple enough. I put in my 1 cup of room temperature water, put the mix in, then the yeast. I used the Basic cycle for my 1.5 lb machine, per the bread mix recommendation. The Basic cycle on my machine is 3 hours, 50 minutes. I've had hit-and-miss success with mix bread in the past, so I stayed up to keep an eye on this loaf. I checked on it with about 1:30 to go, looking through the window - not opening the door. I could see that the loaf had fully risen, and was encouraged. However, when I looked back at it with only 0:30 to go, I was more than a little disheartened to find that the top of the loaf had collapsed. I went ahead and let it finish. I took it out just a few minutes ago, and it's on the cooling rack now. The loaf generally looks OK, except for the concave top.
So, what happened? I don't think it was bad yeast, since I know the dough rose properly prior to baking. I used particular care to ensure the water was right at 80°F, as I recently killed the yeast on a loaf by using water that was too hot.
In the meantime, I'm Googling the hell out of this, but so far haven't been able to find a decent link for bread failures or troubleshooting. Thanks in advance for any help, ridicule, irrelevant cartoons, grammar critique, speculation about my ancestry, pictures of tape measures or advice.