It's just a matter of Resetting the Settings inside the options for that tool. It's just a matter of using the option-box next to the menu item (the little square to the right), then going to the Edit menu and selecting Reset Settings.
1) Just hit f4 (modelling menu hot-key)
2) Go to Create->NURBS Primitives->Sphere (option-box)
3) Edit->Reset Settings.
Here's a pic.