InsertManagedAccount returns null on successful insert

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Create a ContentForShoppingService for a multiuser account
2. Create a new ManagedAccountsEntry
3. Add the new account with InsertManagedAccount 

What is the expected output? What do you see instead?
The account with the id populated.
It just returns null. 
Looks like the cast from AtomEntry to TEntry on line 502 in Google.GData.Client 
(clients\cs\src\core\service.cs) fails.

What version of the product are you using? On what operating system?
Same result with the 2.2.0.0 dll from NuGet and when built from source (r1216).
Visual studio 2013, .NET version 4.5.1

Please provide any additional information below.

Original issue reported on code.google.com by [email protected] on 21 Feb 2014 at 10:56