YouTube API v3 with OAuth2: update and delete fail with "Insufficient Permission" error

I am trying to update and delete videos using the YouTube API v3 with OAuth2 for authentication via the google-api-client (0.6.4) Ruby gem. However, when I attempt to execute either of these two actions, I see the following error message:

Google::APIClient::ClientError: Insufficient Permission

Here's the odd thing: Using the exact same authentication procedure as with update and delete, I can insert (upload) successfully, no problem! So, I do not believe this is a problem with my authentication setup, but somewhere else in my code.

My read-write scope is always the same across any of these actions:

https://www.googleapis.com/auth/youtube https://www.googleapis.com/auth/youtube.upload

And according to the API documentation, that space-delimited set of scopes should cover insert, update and delete actions.

My client_id, client_secret, refresh_token are always the same for all these actions too -- so, that can't be the problem either, can it? Note that my program automatically obtains a new access_token when it expires, so, again, I do not believe that is where the problem lies.

To compare, here is what my insert (upload) code looks like (this works):

# Auth stuff, then...@client.execute!(  :api_method => @youtube.videos.insert,  :body_object => body,  :media => Google::APIClient::UploadIO.new(file_path, 'video/*'),  :parameters => {'uploadType' => 'multipart',    :part => body.keys.join(','),  })

And here is what my delete code looks like (this fails):

# Auth stuff, then...@client.execute!(  :api_method => @youtube.videos.delete,  :parameters => {'id' => youtube_id,  })

What am I missing? Unfortunately, the YouTube API documentation for delete does not provide any examples, so I've got nothing to compare against. Please let me know if there is further information that I can provide to make my question clearer.