I don't think there is anything wrong with your installation. Both screenshots of the shadow render element look wrong to me (could be a VIZ bug or limitation).
I would recommend to start with a fresh scene to get yourself familiar with the way render elements work in VIZ. Just start with an empty scene and put a simple sphere in it. Apply a material that produces a strong highlight. Add a plane and a shadowcasting spotlight. Then experiment a bit with the shadow render element (Diffuse and Specular too).
If that works you can start to figure out what is different in your original scene and makes the shadow render element fail.
Possible problem sources:
- high render resolution (try a much smaller resolution, just in case you are running out of memory)
- exposure control (try disabling if used)
- lights used in the scene (try using another light type, shadow type)
- material type used (some materials don't support render elements properly, try a standard material instead)
Render Elements and Plugins:
There are very few plug-ins that come with their own additional render element types that are specific to the prodcuts features(e.g. Liquid+, finalToon, finalRender).
For general assistance with render elements the commercial plug-in psd-manager allows to output the render elemnts as a PSD file. It takes out a bit of the hassle to get all the render elements into Photoshop, order them, applying the correct blending modes, taking care of premultiplied alpha... Another usefull part of psd-manager is that it can produce a lot of selections for the objects and materials in one go too.
The videos on the site may be even interesting if you don' care about the plug-in itself.
Daniel