Try this.
http://download.cnet.com/Orbit-Downl...-10600926.html
I found out about it in the past week and it works great.
Not so much for the download Manager (Orbit) but for this add-on that attaches to your browser (
Get It) ... Whenever it senses a video or flash video playing in the background, it gives you the option to download it. I was able to get flash videos that didn't work with "Stream Transport" (which is also very good). Only drawback is you have to let the videos play through all the way to the end in real time.
Give it a try.