Firstly, are you IMPORTING a PZ3 file? The is a bug in Poser 7 that when you IMPORT a PZ3
instead of opening it, it has one VERY bright light and deleting any of the lights would crash 
Poser. Don't know if SR1 fixed this. As far as I know, if you OPEN the file instead of using the 
import function, the bug doesn't kick in. If you ARE using open, then I'm afraid I don't know, as
this problem usually occurs with import only. I hope it helps.

Greywolf