You may need to set numpasses. numpasses sets the number of login passwords you can have, so if you have "set numpasses 5" you can have 5 op passwords, oppass1 through oppass5. oppass#level sets the level of the login, 50 being your basic map changing capabilities through 150, which lets you change just about anything on the server.
For example:
set numpasses 2
set oppass1 "cat"
set oppass1level 50
set oppass2 "bear"
set oppass2level 150
If you type "login cat" at the console, it will op you in at 50. If you type "login bear" at the console, it will op you at 150.
Also, if you're putting these in a config file, you need to make sure you exec that config file when starting the server.
As for the server freezing, how are you starting the server? Is it a dedicated server? If so, can you execute any commands at the console? For example, try "map midnight" and see if it changes the map.