I tried this because I wanted to trace the animations in a jazz script. First, I loaded the adult female rig blend that came with the animation i/o tool. Next, I imported the first clip. Then, I imported the second clip and saved it to the copy/paste buffer. Then I switched to the first clip in the properties panel and moved to the last frame in the timeline. Then I pasted the second clip at the end. I thought I had it right, but when I played it back the only thing that moved in the second part of the new animation was the root bone. It looked like when a kid is playing with a Barbie doll. Does anyone here have a clue what I'm doing wrong?

You may have not copied all the keyframes for every bone. Hard to tell from you description. But it is indeed possible, it is how i made the pool slide animations.

Yes, that was it. I didn't select all the bones, only had the one bone selected, so the rest just went along for the ride. lol