TNSLSNR for Solaris: Version 2.3.4.0.0 - Production
NL-00462: error loading parameter file /var/opt/oracle/listener.ora
NL-00427: bad list
NL-00427: bad list

If I do this for the ORACLE8 user I can start the listener.
Strange!
:-)

Check for mismatched parenthesis in the listener.ora

If that was not the problem then it might be this: set $TNS_ADMIN to a specific directory and place the SQL*Net configuration files in that location.