Error starting RRAS

When I try and start the Routing and Remote Access service on my W2k Pro PC I get this error =
Could not start the Routing and Remote Access service on Local Computer. The service did not return an error. This could be an internal Windows error oran internal service error. If the problem persists, contact your system administrator.
In the system log in event viewer it says = The Routing and Remote Access service terminated with service-specific error 505.
I am running service pack 2 and have never used RRAS before on this PC. The RPC service is running.
Please help!!!