If you are trying to do an object discovery in System Center Operations Manager 2012 and it just runs and runs forever, you have probably hit a well known and frustrating issue that has been present in the product since its earliest version. I have no idea what causes this issue, but I do know how to fix it.
Stop the 'System Center Management' service
Delete (or rename _old) the folder:
E:\Program Files\System Center 2012\Operations Manager\Server\Health Service State
(adjust the path to suit your installation directory)
Then just restart the service, the folder will be recreated for you and everything should be fixed.