That can happen with a bad code also, even if you don't have it turned on.

Best thing to do is to get NPR all set up and press X or square on the ones you want on, but wait till the game starts before pressing the note button. If after you press the note button your game and/or PSP freezes then you have a bad code.

But I said I would give you am install tut, even though it doesn't seem you need it now. lol
But here it is.
http://www.megaupload.com/?d=56BQYI3M

it is very short DL less than 10KB. And remember DayPR=NitePR