Here's what I found out after playing around with the keyboard for about an hour last night.
I opened up device manager and kept on eye on how the keyboard was being detected when it was being attached/detached. It turned out that it was being recognized once in about six tries. Even if I rebooted or did the two-button shut down with the keyboard not detected, it failed to be recognized again. If the keyboard happened to be recognized, sometimes it would suddenly disappear from device manager if I waited a minute or two. Not always, but about once in 4 or 5 detections. When I rebooted with keyboard detected, sometimes it would hold, sometimes not.
I tried the attach/detach experiment one more time before writing this post and the keyboard detection rate seems to be much better, about once in 2 or 3 tries. Once detected, It hasn't disappeared.
I'm really weary about this. I shouldn't have to worry about the keyboard konking out in the middle of working on a document. I'm going to report my findings to MS CSR and see what they have to say about this. I have an open ticket with them when I first reported this problem a couple of days ago. I'm also going to try to get to an electronics store and see if I can reproduce this problem with another machine or keyboard.
This keyboard detection problem started about a week ago, a couple days after a Windows update. I noticed the keyboard not working suddenly and it gradually got worse to the point that no how many times I rebooted, it wouldn't come back online. I've experienced this problem before the update as well, but not nearly as often, and it was always fixed with a reboot. If anyone has any ideas from what I've reported, I'm all ears...