I wonder if you use one of the multi-camera views in the Pose Room? Whenever I start a render from one of these views I get the same thing - it goes through loading textures etc and then stops with a blank grey document window. I just switch to the full-size single camera view and restart the render, and it works fine.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)