The easiest (and the only way i know of) way to deactivate your PS3 from your Ps3 is doing this button sequence QUICKLY.
up up up up
Your account info should pop up, with the option to deactivate. Hope this helps.
I can't deactivate any accounts that have ever been on my PS3 from the computer, always had to do it this way.
WOW a mortal combat code lol
Hold start and select as soon as you press x on the netflix app. this is much faster and easier