Haven't been around in a while and just saw that Shawn and Lee released this. It's been a while since I worked on the code, but you're problem Jeroni is actually fairly simple. Diggis is right, the only change that the query box about
night windows on your first startup makes is to the menu, removing some clutter if you won't be using nite windows.
However, your problem I think comes with mixing up
night windows with
nitelites. The object you named a nitelite is a polymesh according to the error message, but only light objects can have the nitelite prefix--as specifically only lights have the 'on' property. The lack of that property in a polymesh was the cause of the error.
Setting a geometric object to have the old style night textures by contrast doesn't require any special prefixes, only that it be enabled for the object using the night windows UI. That said, since I have Max 8 where the old night window textures cause a crash anyway, I haven't been able to test that they are compatible with the alterations in rendering script, so they may not work with my script anyway in earlier versions. I have no way to check myself, and it's not a high priority as night libraries are more stable, more useful, and I've already built in the support for them for all rendering methods(night windows--if they still work at all--are only enabled in the old 3-pass render).
nitelites on the other hand
should be fully functional for both simple and parametric lights in older versions of max to my knowledge. If anyone runs into any problems in older versions however, let me know, a simple fix could be in order (Autodesk changed the property names around a bit over time as I recall).
I'll try to be around here to provide support, gather up some of my previous BSC posts on features, etc., and given time might also complete the help files for download.
EDIT:
catching up as I read here.
Shenti--As Cal said, if you can provide a screen shot of any error messages received, it'll help. Hopefully Andreas will be around to translate this for you and vice versa

.
Chris