I had originally installed Parallels 9 and then wanted to remove and reinstall it. On trying to install it a second time, I received error 15380. Apple Support was able to guide me through using Terminal to verify that only root is using the UniqueID 0, so the issue is not with multiple IDs using 0, which is described here: http://kb.parallels.com/114703. I have not installed any Anti-virus or Firewall software since originally installing Parallels 9 successfully the first time.