I found why nessusd can't start in knoppix 5.1

When I started nessusd I can see this message.

root@Knoppix:~# nessusd
Loading the Nessus plugins...Open /var/lib//nessus/nessus_org.pem : No such file or directory
....

I think that "/var/lib//nessus/nessus_org.pem" is wrong directory.
Am I right?

So where can I fix it?
What scripts do I edit?