I tried this too as I often get this error.
In my case this happens when I have a map based on the Dungeon templates but you try to use a CC3 tool such as land mass or rivers (on battlemaps etc). Like NeonKnight, I also cannot get the error to happen using the same template.

I have had terrible trouble getting DD3 to work correctly on my Vista machine, but I found that uninstaling DD3 and reinstalling it with the latest v7 patch has helped a lot.


I found that working through the DD3 manual gives you the basics and there are some excellent tutorials (and lots of helpful people) here to help you take it further, so dont give up

edit: just a thought, but does it happen with a predefinded template?