Problem with the warning screen?

Hi, I have integrated the latest 1.4 Oculus SDK into our software and I'm experiencing a problem with the "Heath and Safety Warning" scene.  (The scene where you have to look a the 'ok' button for 2 seconds in order to dismiss the warning and continue on to our content).

I'm getting a mostly blank scene with an hourglass visible.  If I look around "behind" myself, I can see a frustum-shaped-chunk of the grey-grid scene that is the backdrop for the health and safety warning.  Head tracking is working smoothly but the 'grid-scene' appears to have been clipped for a camera frustum facing backwards and is not being updated.  So if I look forwards, I just see blackness and as I look around I can see that frustum-shaped-chunk of the grid scene floating in space.  Unfortunately I can't see the button when I'm looking in that direction so I can't get past this scene.

This is entirely possibly my fault but I've checked the return values from ovr_CommitTextureSwapChain and from ovr_SubmitFrame which are both returning 'success' and I've verified that all of my normal draw calls are being executed (used nVidia nSight to inspect them)  

Thanks for any help!