There's no need to link anything having to do with your YouTube channel to the same account that's used for the Cloud (Developers) Console. It shouldn't hurt, but it's not necessary.
Ensure that you go through the OAuth 2 flow using the credentials of a valid YouTube channel (which, again, doesn't have to be registered with the Cloud Console) and that you choose the appropriate option if you see the OAuth 2 channel picker (see http://apiblog.youtube.com/2013/06/google-page-identities-and-youtube-api.html)
If you're still having trouble, try this as a sanity check: use the API Explorer to make a youtube.channels.list(mine=true, part='snippet') call, and authenticate with the same credentials using the little OAuth 2 toggle switch in the upper right. Do you get a response back?