I had same problem and have posted a solution here (there is an ANT script referenced which can be downloaded):
http://ironclaws.wordpress.com/2012/06/18/jbpm-5-2-tomcat-7-mysql-ant-script-18-2/
To summarize what is required in order to install jbpm 5.2 onto tomcat 7 using the final full distribution:
Bitronix Transaction Manager : The distribution does not attempt to deploy / configure this despite the requirement. The above Ant installer will install Bitronix at the Tomcat Server level – advantageous as at this point BTM may be integrated into other projects on the platform.
The jBPM distribution is designed for JBoss AS server and the console / console-server packages include EL (expression language) libraries. These will conflict with those which are installed with Tomcat – the Tomcat EL should be preserved.
There is some confusion with respect to javassist jar in the config / config-server distributions.
The included jars should be dropped – and included into both config / config-server javassist-3.4.GA
The reason for this dependency is that Hibernate 3.4 is deployed as persistence layer in this distribution.
There is a conflicting dom4j library – dom4j-1.6.jar deployed with the console / console-server packages. This should also be removed.
It is not mentioned clearly that the parameter:
-Dreporting.needcontext=true
needs to be passed to the Tomcat JVM in order to allow the gtw-server to correctly instantiate the report module loader.
For the ‘Demo’ it is important to configure the human-server persistence correctly, and additionally address the includeantruntime issue during starting of this service.