And each time you create a light, it should create a corresponding shadow camera for it.
So what you might have to do is delete the lights that don't have shadow cameras
and create new lights to take their  place.
Really, with Poser 6 you only need two or three lights anyway.  One set to
Ambient Occlusion and one to  generate shadows, and maybe another
for highlighting something.  Over the years people have gotten light
happy in an effort to simulate global illuminations, and so people ended
up with far more lights than they really need, which take up resources
and really bogs down rendering times.
You didn't say how many lights you were using, but you should ask
yourself, do I really need this light?  Do I really need that light?
Maybe a good thing to do would be to get rid of all the lights first,
then set up one for Ambient Occlusion and see how your scene
looks.  Then add another for shadows and see how you like that.
Then add another one if you really need it.