You are getting following error on Domino server.
"HTTP Server: Error - Unable to Bind port 443, port may be in use or user needs net_privaddr privilege"
Diagnosing the problem
Start Windows task manager, go to View -->Select Columns --> Select PID (Process Identifier).
Issue command "netstat -ano" from Windows command prompt. This will list the PID against the port 443.
You will find PID as 4 which points to Windows "NT System & Kernel" process. This will tell you which process is holding the port 443.
Resolving the problem
In one particular case, problem resolved by stopping the Windows service "Secure Socket Tunneling Protocol".
This service has dependencies on the other services as shown in below screen shot, which also need to be stopped.