Alright, this seemed to be a locale issue. After I changed my locale to yours, I got the same error. Apparently, the current data is written out and in some languages this might include characters which aren't accepted by the XML parser. So I changed the output data to dd/MM/yyy and now it seems to work. I committed this so it will be included in the future, but if you want to try it out locally, simply do this change to your source code:
https://github.com/krisv/jbpm/commit/c7bef4e9914efcdebff3a649fd80714a1600d3eb
Kris