[O] Problems PlantUML

[v]

Hi,

running Org-mode version 7.8.11 under GNU Emacs 23.4.1
(x86_64-pc-linux-gnu, GTK+ Version 2.24.10) I am stumbling over a
problem with babel/plantuml: Exporting a file with simple demo data
leads to a png file with error msg "@startuml empty
description". Evaluating the code block results in a correct
diagramm. Where am I wrong?

Thank you in advance

  Volker

BTW: Thank you for this great tool!!