Vista - Cmdlet, CallBacks and EndProcessing

Hi

I have a component that listens to a real time feed.
When a message is received it fires an event with a custom EventArgs.

Here is the problem. Question is how I can get around these both in a cmdlet
and optimally a script.

1) I wrote a cmdlet and overrode EndProcessing. I set up the component and
the callback [1]. When the event fires, this exception is thrown:

The WriteObject and WriteError methods cannot be called from outside the
overrides of the BeginProcessing, ProcessRecord, and EndProcessing methods,
and only from that same thread.

[1]
listener.OnMessageReceived += new
EventHandler<MessageEventArgs>(listener_OnMessageReceived);

void listener_OnMessageReceived(object sender, MessageEventArgs e)
{
Write-Object (e.Message);
}