A few days ago, i have setup an Oracle 10.2 on HP Tru 64. I have installed Oracle with oracle user. Then for some reasons privilleges of $ORACLE_HOME directory has changed. When clients wants to connect database via listener, they got ORA-27140: attach to post/wait facility failed and ORA-12518: TNS:listener could not hand off client connection errors. I solved the problem with changing rights of $ORACLE_HOME/bin directory as chmod 6751 oracle.