MySQL wont start after modifying /etc/my.cnf I have Linux Red Hat 5, with Zend Server and MySQL Server installed.

I am trying to change the default MySQL port to 512.  However, after making this change, MySQL will no longer startup.  I get the error below:

Starting MySQL...The server quit without updating PID file 
    (/var/lib/mysql/localhost.localdomain.pid).


How do I resolve this issue?
You say that you are trying to change the MySQL port from 3306 to 512.  If that is correct, then then problem is that all *nix (Linux, Solaris, AIX, etc) require you to run as root in order to bind to ports below 1024.  

Try running it on port 3307 or something.