I fixed the ArrayList and custom class problem. The C# example has been changed to make a test method for arrays (ArrayList, StringCollection, ). There is also a test for a custom class. (Note: currently there is no support for classes that inherit from CollectionBase, I will have to check how to do this in JSON.)
Update: You have to mark your own classes with the [Serializable] attribute. See the example at the download website.
Download available for free at http://ajax.schwarz-interactive.de