In the documentation on mixins you mention the file "tests/mixin.lzx". That's not part of the distribution, but only available when you check out the source code. http://www.openlaszlo.org/lps4.9/docs/developers/class-inheritance.html#mixins
You might want to include the file in the distribution, or point the file in SVN, e.g. http://svn.openlaszlo.org/openlaszlo/trunk/test/mixins.lzx
