Hans, I got the same error message at Sweet Home 3D launch under the Ubuntu virtual machine I test it, so I don't think it's so important.
I've tested again the tree file and if the import wizard was able to handle with no problem, I discovered that Sweet Home 3D hangs too after the importation on my machine. So I guess it's an other bug I'll have to fix...
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Emmanuel Puybaret, Sweet Home 3D creator
