disable screen lock on macbook pro running lion

Screen Lock is when the screen locks after being inactive for the period you originally set - the thing is that I did it through the System Preferences -> Security but now the option to undo it is inactive - is dimmed...

I did but even though it gives me the choice to change password - which i did - it does not give me the option to disable this option...probably is a bug that is why i asked for help...

we were on the same screen but the option "Require..." was ticked but dimmed...I could not change it...so I restarted and everything is ok now...THANKS a lot for the help!!!