Ok I'm playing with some Silverlight and with WCF. And while if you stick with the standard stuff it works great, but if you want something special you get trouble. And I wanted DUPLEX communication. Ok more on that in a later blog.
Here is some cool code I used to Serialize/Deserialize some off the communication I'm doing between Silverlight and WCF.
It uses generics, introduced in .NET Framework 2.0. Let me know if you can use it.