Nulls returned in Async WCF queries

I'm talking about client side async calls -- i.e. when you use svcutil /a to generate async methods for your WCF service. This is usually rare, but happened to me yesterday -- I was getting nulls back in the EndResponse. I tried a lot of things -- dug up a lot of documentation on how WCF does async under the covers, reformed my responses, tried changes to asyncstate etc; in short spent a lot of time. But the fix was --- had to update the proxy -- that magically started returning entities and got rid of the null refs.

Sometimes the simplest problems take the most evil form.

So, wanted to share my thoughts just incase someone has a similar problem