Finally I downloaded the videos. Now I know where the issue is. I have slow connection, token is changed during download and I won't be able to resume the download. Thank you so much for your help.
But if someone has any idea how can I download this video:
http://www.bbc.co.uk/programmes/p00zgkcl
in high quality (1500kbps, I only got 480) I'll be many thankful.