How can i upload a project from imovie to youtube?

When i upload an imovie progect to youtube starting from:

> imovie > share > youtube > account name and pw

an advise says 'account name and password incorrect'.

I uploaded this way loads of videos since a mounth ago: i put no tags and 720p res and it always worked.

My account name and pw are correct: i can still upload imovie videos from my iphone.

Any help is welcome!

Thanks