I'm not sure if anyone picked it up, but the Youtube module does not work entirely with silverstripe v2.3 onwards.
This is most probably because the youtube module uses reserved words, eg: method user query. My guess is sliverstripe v2.3 went through some clean up therefore conforming to best practice.
My recommendation to programmers do not use reserve words, check mysql docs for more info on reserved words.
It would be nice though if the exception handler to give some kind of message to convey you are using resrved word.
Anyways, to get around this problem for now you need to change Method, User and Query in youtubeGallery.php to something else eg:yUser. Also change the column names in the DB to the same name as in youtubeGallery.php. This work around works, but it does give a save error in CMS. So not entirely bug proof. I recommend the youtube module programmers to look into this ASAP.