You are attempting to configure a Discover Scan with Quarantine. The incident is detected but the quarantine fails with the error: "Network layer error: A duplicate name exists on the network.."
Another computer in the network is already using the (host name used by NetBIOS) name of your computer. Sometimes you may receive this error message even if your computer has a unique name.
The reason is the outdated WINS Server. It is because WINS server is responsible for verifying the NetBIOS names of the computers in the same network.
Change the NetBIOS name of the machine and reboot. Check the WINS server for duplicate entries. OR Use the IP address.