>> We actually found out that the problem is caused by an unnamed lane. << Could you please raise a jBPM Jira for this so we can fix it? Lane names should definitely be optional.
>> will it be possible to run Guvnor and Designer on an IP different from localhost and a port different from 8080? <<
This was already possible in Designer versions prior to 2.0 - see here for now: https://hudson.jboss.org/hudson/job/jBPM/lastSuccessfulBuild/artifact/jbpm-distribution/target/jbpm-5.2.0-SNAPSHOT-docs-build/jbpm-docs/html/ch10.html (specifically chapter 10.5). The Guvnor configuration part however iirc is available in Guvnor 5.3.1 + so if you are using prior versions it may not be possible.
Hope this helps.