What is the exact error message you are seeing in the event log for port 1812. As previous entries indicate, the Policy Manager uses port 1812 by default for RADIUS communicate with the enforcer. Other products use port 1812 as well such as the Windows IAS RADIUS server. If you don't see port 1812 when doing a netstat -a or you've already changed the port from 1812 to some other number, then it's quite possible that the issue is related to something else other than the Policy Manager. I would recommend starting with the error in the event log for port 1812.