Hi,
i used External Lightmapping Tool, and made it worked perfectely, every thing is well baked in my scene. I just add a new building, and tryed to use ELT. Nothing starts…the tools doesn’t pop-up and i get a little warning : “NullReferenceException” talking about Calcarea.CheckIfNormalized…
If someone knows a bit more about that…
Thanks
Tom
Hi Tom and welcome on Unity Forum 
Thank you very much for your feedback.
I’ve just looked up the problem and made an update, so that in the latest version (1.2.3) the problem no longer occurs.
You can download it from my blog or from here:
http://code.google.com/p/unitylightmapper/downloads/list
Works fine, thank you very mucj !! What a fantastic way to get a problem solved, from the dev himself!! Thanks again, you make my life simpler!