Rendering Reflection only is not possible

[Ron Martin]

Create a simple scene with just an open tube. Set a V-Ray Material with black diffuse, high reflection, glossy 0.6 ,fresnel off. No lights. Put any simple map into the reflection environment of the v-ray render dialog. If you render with gi=on it looks fine.
However in IPR the scene is rendered black, only alpha is present. In material editor, f you just touch any parameter of the reflection map, the RGB rendering pops in.
If you switch off gi, the interior of the tube will be rendered superbright and rendertimes get quadrupled.

[hermit.crab]

Can you render the scene through the standalone application (right-click on the viewport >.vrscene exporter > export and render) and see if the issue is still present? Most likely you would need to turn off the 'Default lights' in the global switches rollout.

Also, what version of V-Ray are you using? I cannot seem to replicate the IPR behavior you mentioned.