OK, using PP 2012. Here's a sequence of images showing what I see...

 

This is the room as it loads, with the pre IDL lights active...

 

Same scene from outside. It's a very big scene overall, with lots of objects. Computer handles it just fine. My old laptop handles it fine...

 

Then I run Scene Fixer with these settings. Note that ambient and translucent values are to be set to zero for the whole scene...

 

  then I delete the lights... and get this;

 

I won't post the materials for the several hundred things in the scene (if not thousands), but I did select the couch to show as it seems to be glowing more than other things, and it should be dark by its colour...

 

 

Thanks for the replies so far, BTW...