try this:
on ^1:SNOTICE:*:{ haltdef }
and see if that helps, ALT + R in your mirc, then paste that line, click OK and youre done.
and check the "show notice" again in your mirc options.
I guess you using a script? try this if my code dosent work:
//mode $me -s
if that helps, then one make your script adding the +s mode to you, and then you see the server notices..