Silverlight MSCRM Dashboards - SoapHelper throwing "Object reference not set..." errors

So, you've created that shiny dashboard using Silverlight. You're using the SoapHelper provided by the SilverCrmSoap library. But any time you try to hit Dynamics you get a big dirty "Object reference not set to an instance of an object" error. What could be going on?

In the associated HTML page that loads the XAP file make sure you've referenced the correct javascript library:

<script src="../ClientGlobalContext.js.aspx" type="text/javascript"></script>

9 times out of 10 you'll have referenced the Silverlight.js by mistake. I keep falling into this trap. I must have a memory like a sieve!