>> when I used ant start.demo, jboss failed to start within 5 minutes so it failed << this is really an issue with jboss as 5.1 taking ages to start up. I typically replace it with jboss 4, but anyways, you can increase this value in $jbpm-installer-dir/build.xml, change default:
<waitfor maxwait="5" maxwaitunit="minute" checkevery="30"....
to like
<waitfor maxwait="10" maxwaitunit="minute" checkevery="30".....
>> when I tried to go to http://localhost:8080/jbpm-console I got the error above << what is this error? Increase the maxwait value in build.xml and run ant start.demo again (make sure there are no already running jboss as instances present) so that the server and task service can start up fully, then try again and let us know if you still run into issues navigating to the jbpm console.
Hope this helps.