There are no permission problems, I installed all twice by unzipping jbpm-5.1.0.Final-installer-full.zip and running ant as described in install page. Home is c:/users/Sperkmandl/jbpm-installer
I'm running win- 64 bits with 4 GB. And of course now (after yesterday reboot) everything seems running fine, except about the (XSRF attack?) log error, which appears often in today log (whatever it means).