AFAIK this is just a DEBUG level message. Do you see anything in the server logs? Maybe something happenend during the download of jboss as..you could try to:
- go to $jbpm_installer_dir/lib and remove jboss-5.1.0.GA.zip
- go to $jbpm_installer_dir and run "ant clean.demo", then "ant install.demo" ..this should download the AS again
- run "ant start.demo" ... and watch the server logs in $jbpm_installer_dir/jboss-5.1.0.GA/server/default/logs/ (server.log)
Hope this helps.