Thanks Laurent.
Basically, another program "hook" has to hijack our OpenGL context and take control of it for a time, rendering stuff and at the moment, because we use offscreen textures, there is no way for the hook to know which is the real screen, and which is our offscreen texture.
So, either we need to know which is which, or not use any offscreen textures (which is probably impossible for us as we do some quite advanced things).
Thanks
Ed