ircd port 6697 error on new (Windows) install

The services logged error is:

1/2 05:10:00p 0000 IRC !Error Error: Unable to add host to socket set creating listening socket on port 6697

And another error is (confusingly) logged to the terminal server log (where all Socket object errors get logged):

  1/2  05:10:00p  1592 !ERROR 48 binding IRCd socket to port 6697: Only one usage of each socket address (protocol/network address/port) is normally permitted.
  1/2  05:10:00p  SSH ERROR 'Couldn't import the session key used to protect the private key: Couldn't unwrap encrypted key' (-22) getting private key from bbs_thread