in .net 2.0 serialization security has been upped. In other words, by default, bags won't be serializable. You will have to explicitly allow it by setting some property on your channel.
This is how I used to start my serverchannel:
Code:
BinaryServerFormatterSinkProvider serverFormatterSinkProvider = new BinaryServerFormatterSinkProvider();
serverFormatterSinkProvider.TypeFilterLevel = TypeFilterLevel.Full;
IDictionary props = new Hashtable();
props["port"] = 1200;
TcpChannel chnl = new TcpChannel(props, null, serverFormatterSinkProvider);
ChannelServices.RegisterChannel(chnl);
I hope that helps!