If you cannot make opmn run during soa installation and get some irrelevant errors on ui and see this error log on opmn.log, do not worry:) You can handle this issue with an easy configuration change on db.
I faced this error when db and soa_suite are designed to be running on the same server. And most probably the default ports are conflicting.
Go to the ons.conf which is under opmn conf of your db_home. Change the settings from "localport=6100 remoteport=6200 loglevel=3" to something like "localport=7100 remoteport=7200 loglevel=3" (of course if they are not in use!). Restart the listener.
Retry the soa installation and enjoy!!
