The listener.ora file was copied from a previous version of Oracle.
The file contains different syntax for the database and environment
variables. When you try to use this file with Oracle v8.0.5, it
cannot understand the parameters listed in the listener.ora file.
One possibility is that your original listener.ora file got deleted from OS. And when you started the listener next time, it got created with default parameters, which weren't as per your original listener's parameters. It could also be that your original listener's name was something else from the default LISTENER.