what java version do you run on? If it's 1.6 there could be an issue with deployment order of web applications - dashboard relies on tables created by jbpm console and since by default it uses in memory data base they might not be created in time. So what could suggest to try out is to first disable deployment of dashbuilder )by adding marked file in deployments folder jbpm-dasbuilder.war.skipdeploy) and start the server. Once server is up and running rename the marker file to be dodeploy instead of skipdeploy and then dashbuilder will load.
Alternatively you can try on java 1.7 or change h2 data base to be file based instead of in memory.