FLEX: Was expecting mx.messaging.messages.AcknowledgeMessage, but received null

Using RubyAMF with Flex.

response = HashWithIndifferentAccess.new( :handle_type => HandleType.first ) works fine, and HandleType is a model in our rails app.

response = HashWithIndifferentAccess.new( :user => User.first ) borks, and the response I get in flex is:

"Was expecting mx.messaging.messages.AcknowledgeMessage, but received null"

User is just another model in our rails app, but obviously there is something different about it. The ClassMapping is set up identically, but 开发者_JAVA百科with the correct names and attributes. Any ideas what might be causing it, or what to look for? I am not even 100% sure I know what the fault means.

Any help would be great!

I guess asking the question here gave me the necessary brain-power to solve this :D

In case anyone is interested, here is what happened:

In the Account Value Object (AccountVO), I had the following:

public var user:UserVO = new UserVO()

In the User Value Object (UserVO), I had the following:

public var account:AccountVO = new AccountVO();

So, it basically got stuck in an infinite loop of creating value objects, and never actually responded! Doh!