I don't have an answer to your question but thought I would share my own observation. If I'm downloading a video file using LW and I preview the file by launching it from within LW, while waiting for WMP to open, the total d/l speed shown will go to way over 1000KB/s(the max speed I've ever gotten is 180KB/s with dsl) but the speed shown for the individual files in the d/l window don't increase. After the preview launches everything goes back to normal.
So I think it might be a bug or LW mistakes launching the preview as an increase in d/l speed
