Hi, what version of the jbpm-installer are you using? The most likely reason for the problem you are experiencing is that jbpm-installer comes with an older jBPM Designer version which is not able to parse the bpmn2 of the Evaluation process.
To upgrade your designer version:
1) in $jbpm-installer-dir/lib remove the designer war.
2) in $jbpm-installer-dir edit the build.properties file:
designer.version=1.0.0.054-jboss
designer.url=http://sourceforge.net/projects/jbpm/files/designer/designer-1.0.0.054/
3) in $jbpm-installer-dir run:
ant clean.demo
and install.demo
and start.demo
Try again with the latest version and please report back any issues.
Hope this helps.