Hi Arun,
Check if you have any other service running at 8080 port,if so then jboss will not start.By default build.xml has 8080 port entry where server starts and
human task server runs at 9123 port.
I don't think any problemrelated to human task service ,because it's started after jboss start command is called for example-
<!-- Start Demo -->
<!--<target name="start.demo" depends="start.h2,start.jboss,start.eclipse,start.human.task" />-->
<target name="anand.start.demo" depends="start.jboss,start.human.task" />
<!-- Stop Demo -->
So check the port and if required you can change the port entry in build file as well as jbpm.console.properties file as well.
Thanks,
Anand