This problem often (maybe not always) comes from missing parts

in the light set (LT2) file. 

If the author built the LT2 by copying and pasting sections

of a simpler file, he generally fails to include those ShadowLiteCam

thingies.  One ShadowCam must match each light.

When Poser deletes lights manually, it seems to handle

missing Cams. But in Python the missing cam causes a problem.

An LT2 that was made by creating and setting all the lights inside Poser

and then saving to library, will always work properly.

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