>hm, when I explicitly add j3dcore.jar to the build path of my eclipse
>project, the error disappears.
>That is good, but strange since it worked without this on my Laptop. And
>I definitely have java 3d installed because the 3D heatbugs start
>without problems if I start the console via mason\start\mason.bat.
>But anyway, I am not really using 3D stuff, so I will ignore this
>error/bug/warning and get on with my stuff :-)
>

This is probably because, on your laptop, you installed Java3D as an
installed extension (libraries in the ext directory of the JVM), which means
they are 'natively' seen by all Java applications. The Windows installer
does this by default, even though it's actually not recommended in the
Java3D README.

See, for example:
http://docs.oracle.com/javase/tutorial/ext/basics/install.html

Regards,
Stuart