I have this fully enclosed room here. Actually it's the primitive box, just scaled up quite a bit. I placed four lamps on the ceiling, each has a point light positioned directly under it.The four point lights are set to 75% intensity each and are having inverse square fall off.

The result is this (attached image, reduced img.size by 50%, to post it here)

While setting the point lights to "constant" attenuation, the room is lit very even ("constant", so to say ^^ ), but with setting them to inv.sqr fall off, there are appearing these brighter splotches.

The render has IDL enabled (the settings are 1500 samples, 8 bounces and IC set to 50)

Is there a way to reduce, or even eliminate the bright areas, with an inv.sqr light setting?