The VSO API sample gives bad request for the build queue api call

Hi,

I've been attempting to use the VSO API with my VSO account for a while and i always get "BAD REQUEST" / 400 for anything apart from GET cals.

Today i got the same response when using the sample code in the Q&A section on http://www.visualstudio.com/integrate/get-started/get-started-rest-basics-vsi 

Can someone tell me whats wrong? Do i have to enable anything on my VSO?

Thanks