There is a work around to do this (am not sure how ethical this is). Since it works am sharing the same.
1. Disable Flash in your browser (preferably use FF)
2. View video in HTML 5 mode (ex. http://www.ml-class.org/course/video/html5embed?videoid=1)
3. Right click on the video frame and select "Show only this frame"
4. Right click on the frame and select "Download with DownThemAll" ...