A couple of thing to help determine the cause:

Are you using the GPU? If so then turn GPU acceleration off
Do you have a light visible in the frame? If so switch the tonemapper to linear and adjust the exposure. If a light is in the frame the autolinear tonemapper will adjust the exposure for the brighness of the light with the result that the rest of the scene plunges in darkness
Are you using the Studio Cubed? If so check the camera, it's likely to be outside the Studio. Make the backwall of the Studio transparent or move the camera inside.

btw, when you click on "Render frame" from Reality you are exporting the scene to Lux.

Hope this helps.

Forum: Poser - OFFICIAL

Subject: Reality 3 -- Black Output Screen?