i'm having big issues here...
1. if you put an object with a light material into the light-select, only this object is used.
instances are ignored and must be added separately to the light-select.
2. if you have the object with the light material in a group, you can put the group instances into the light select.
but for the master group this does not work and you must add the actual sub-object having the lightmaterial into the light select.
this is quite tedious... specially when you have more complex setups... lets say:
you have a group called "lamp1". inside is an object "bulb2" having a light material
now "lamp1" used 2 times in a "car", but there is also a "lamp2" and the car is instanced multiple times.
now light-select for lamp1 wouldnt work without breaking up the car symbol, because car has different lights in it.
in short : PLEASE SUPPORT INSTANCES IN LIGHT SELECT :)
ps...
the whole behavior is a bit strange... as stated in 2. sometimes it works if you add an instance of a group containing a light
but if you add the group itself (not an instance) the contained light does not get added to the light-select...