How to log in with the native YouTube app? I created a new YouTube account to use functions like "watch later" on my iPhone4, my PC and my AppleTV2. But if I try to log in with this account on my iPhone and the native YouTube app, I always get the error message that the username and/or the password are wrong. I used as username the email address I used to create the YouTube/Google account and which I use to log in the web interface.

What I'm missing? I'm sure that the credentials I use are correct.
I had the same problem. Since I have signed up for 2-step verification I must use not my YouTube psw, but a application-specific password. 

You can generate an application-specific password on your Authorizing applications and sites page using a desktop. 

http://support.google.com/youtube/bin/answer.py?hl=no&amp;answer=184968  

Remember to use your email address, not you username. 

Worked for me. :)