Sorry, I misunderstood. 

Render settings look fine.  I see you are using IDL.  You are aware that IDL works best within an enclosure like a room or under a skydome.  Under such conditions, I use D3D's renderer found under Partners within the Scripts menu.  It give you a little more control.  Your Gc is defaulted to 2.2.  With this value, you can render with much less light intensity than you would with previous Poser versions. 

There are some things we can consider, see why previous renders worked and current renders are not working.  Are the same models giving different responses to light?  Are Material Room settings "standardized" and "optimized" for rendering?  I have a tendency of decreasing my diffuse_value to 80% or so, depending on the image map.  This is my optimization of all materials to not reflect 100%, they will render a little darker in response to available lighting, a much more realistic result. 

As mentioned, your light intensity should be lower for all lights created in your scene.  For example, when I create a sunlit exterior scene, I use a skydome and 1 infinite or point light @ 75 - 80 % intensity with Gc and IDL active in the render settings. 

Could you describe the particular scene or scenes which are giving you problems, with as much lighting and set details as possible?  Some screencaps of settings will also give us a better clue.