Authenticated YouTube Data v3 query fails with 403 Forbidden message - youtube-api

Question

This is a c# .NET application. The app makes an OAuth2 authenticated YouTube Data v3 ChannelList query that had been working for two months. Recently, the query fails with a 403 Forbidden message from Google. It fails from our Azure Web server and when running in Visual Studio on a developer desktop. The query works for at least one user but fails for all others tested. The query (listed here) works for all users from within the API Explorer. I cannot find additional error description returned from Google.
Update (7/15/2013): The query now runs after adding the access_token to the query. Previously, it executed successfully with the access_token only in the Service object, not explicitly part of the query. Although the query is successful with access_token directly appended, we are getting a downstream JavaScript error on on the YouTube embedded player. Not sure if that is related. I see there was a .NET API update in late June. #Ikailan, did something change at Google to break the access_token auth in the Service object. Note: we DID update to the new API. Are changes required to our code to use the June 2013 API updates?
Error Message "The remote server returned an error: (403) Forbidden."
Method that was failing but now works with the Auth token added to the query.
//Gets the channel information of the current user
public static ChannelListResponse GetCurrentUserChannel(string token)
{
YouTubeService service = new YouTubeService(GlobalSettings.applicationName, GlobalSettings.developerKey);
GAuthSubRequestFactory authFactory = new GAuthSubRequestFactory("YouTube", GlobalSettings.applicationName);
authFactory.Token = token;
service.RequestFactory = authFactory;
ChannelListResponse response = new ChannelListResponse();
try
{
System.IO.Stream resultStream = service.Query(new Uri("https://www.googleapis.com/youtube/v3/channels?part=id%2Csnippet%2CcontentDetails%2Cstatistics%2CtopicDetails&mine=true&access_token=" + authFactory.Token));
using (var reader = new System.IO.StreamReader(resultStream))
{
string value = reader.ReadToEnd();
response = JObject.Parse(value).ToObject<ChannelListResponse>();
}
}
catch (Exception ex) { }
return response;
}
Line that throws the exception. Added the Auth Key (see code above). Now the query executes successfully.
System.IO.Stream resultStream = service.Query(new Uri("https://www.googleapis.com/youtube/v3/channels?part=id%2Csnippet&mine=true"));
However, we are getting an Access Denied error for an embedded YouTube video player.
A first chance exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll
An exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll but was not handled in user code
Exception was thrown at line 4224, column 4 in http://localhost:49185/YotaCast_Prototype/Scripts/jquery-1.9.1.js
0x800a139e - JavaScript runtime error: SyntaxError
Exception was thrown at line 4242, column 4 in http://localhost:49185/YotaCast_Prototype/Scripts/jquery-1.9.1.js
0x800a139e - JavaScript runtime error: SyntaxError
Exception was thrown at line 360, column 9 in http://localhost:49185/YotaCast_Prototype/Scripts/foundation/foundation.js
0x800a1391 - JavaScript runtime error: 'Zepto' is undefined
Exception was thrown at line 1, column 97 in http://s.ytimg.com/yts/jsbin/www-embed-player-vflXN6WzI.js
0x80070005 - JavaScript runtime error: Access is denied.