Sorry for this problem.
As mentioned in bug #2195417 available at https://sourceforge.net/tracker2/?func=detail&aid=2195417&group_id=152568&atid=784665 , you have to update Java on your system with Java update 2 available at
http://www.apple.com/support/downloads/javaformacosx105update2.html .
I fixed this bug in Sweet Home 3D source code in such a way it works with
an older Java update, but this fix won't be distributed immediately.