Also, if you're pasting out of chrome, make sure you're not pasting a link
So it looks like:
http://www.youtube.com/watch?v=BuhMV2OI_2Ys
and not
https://www.youtube.com/watch?v=BuhMV2OI_2Y
On a Mac, you want ctrl-option-shift-V. I'm not sure what it is on a Winders machine.
EDIT: figures when I want to post an example, it decides not to work.