Ive seen a couple of threads where people expressed frustration in dl youtube videos.
A couple of solutions.
Generally google download youtube video. Ton of sites come up.
One of them is keepvid.com.
Ok more specific, permanent and easy.
On the Opera browser (my fav) you can install a java plug in which puts download links in different quality formats (hd - low def) under each vid.
This plug in works on some other sites.
Heres the link:
Java plug in
Another one which works great is 'clipta'. Clipta is a plug in which works on Firefox. And most all videos work using clipta.
Not its called a toolbar and in my opinion all toolbars are quasi viruses. However this toolbar is barely a toolbar. I highly recommend it.
Clipta DL from cnet
Follow the instructions on each of the above links for Opera and FF. Good luck and happy archiving.