Using Poser 5, I imported a PZ3 scene file into another.  Both had lights.  Ended up with more lights in the scene than originally, so deleted all lights (using Python script), but one light's shadow cam is left behind that won't delete no matter what I try, and when I add any lights, the scene won't render because it gets hung up by that fouled up remnant shadow cam.  Anyone have suggestions how to delete that spurious shadow cam?

You'll probably have to look through the PZ3 manually and find
which shadowcams are tied to which lights.  Might be easier
to redo the whole scene with only the lights you want, now that
you know which those are!

This problem happens fairly often .... Some popular light sets in
the P4-P5 era were written by editing LT2 files instead of building the
set directly in Poser and saving it.  The editing was done by
copying and pasting blocks of text without altering the lines
appropriately....  with the result that the shadow cams were
all tied to one light, and Poser doesn't know what to do with them
on deletion.  (This may not be exactly what happened in your
case, but it's a good bet.)

Oh, wait... if you have only one shadowcam, you can just remove it
easily from the PZ3, and then you'll have a perfectly lightless scene
to start from. 

Look for

camera SHADOW_CAM_LITE
    {
    name    Shadow Lite 2 Cam
    off
  ........
   
then scroll down to the end of that bracketed paragraph and delete it.

There will also be a short paragraph referring to the OBJ file
for the shadowcam

camera SHADOW_CAM_LITE2
    {
    storageOffset 0 0 0
    objFileGeom 0 0 :Runtime:geometries:Camera:Camera.obj
    }

but you don't need to remove that if you're uncomfortable with
deleting stuff.  Poser is already loading Camera.obj for the
real cams, so it won't hurt to load it again.

Thank you Ockham.  I thought of that, but wasn't sure what lines to delete.  Now I know.  In the meantime, what I just finished doing was renaming the problematic light so that it wouldn't conflict with the names of the ones for the newly added lights, and it seems to work, as the scene renders now.

Makes sense.  Poser doesn't seem to mind having extra shadowcams
around, except when trying to delete lights.  That's when it sometimes crashes.