Youtube DirectUploading ASP.NET #2

What steps will reproduce the problem?
1. index.aspx using google data api
2. retrieveing a video works fine
3. uploading causes Google.GData.Client.GDataRequestException: Execution of
request failed:
http://uploads.gdata.youtube.com/feeds/api/users/Moneoneseven/uploads
---> System.Net.WebException: The remote server returned an error: (400)
Bad Request.
deleting and updatinf causes Google.GData.Client.GDataRequestException: Can
not update a read-only entry

What is the expected output? What do you see instead?
upload/update/delete video

What version of the product are you using? On what operating system?
lastest API, ASP.NET 3.5, IIS 7

Please provide any additional information below.
i think there's something wrong with authentification (developerkey,
clientid, ...)
manual upload via youtube-website works fine.