How to change "long_query_time" with mySql 3.23

[thomas Armstrong]

Hi.

I'm suffering a severe slowness of my server (mySQL 3.23), and want to
detect Slow Queries.

I installed mySQL on '/usr/local/mysql', and works ok. But if I insert
this line into '/etc/my.cnf':
-----
log-slow-queries = /usr/local/mysql/log/slow-queries.log
long_query_time = 5
-----
it won't restart. If I comment the second line, it works ok.

Does anybody know how to set the slow queries time? Thank you very much.