In any fly-by-wire aircraft, the computers will return the aircraft to a normal flight attitude. So the A330 has reduced aerodynamic postive stability (still above neutral), but the computer involvement makes up for this. Of course, when you lose the pitots, the computers drop from normal law to alternate law, which means they stop intervening in some situations, and instead warn the pilots. The prime example is a stall - you can't stall an A330 when running in normal law, as the computers will manipulate the control surfaces to prevent this. In alternate law, the computers are unsure of the full picture, due to failed inputs, so they warn the pilots of a stall. In this case, you have lost some of the stability introduced by the computers - there is some stability there, but when you are pulling back on the side stick while stalling in a storm, no amount of positive stability is going to correct it.
Positive stability doesn't fix all situations. If you have too low a power setting, out of trim, CG not correct or even strong external forces (such as a storm), the a positively stable aircraft can fail to stabilise itself.
Think of your car steering wheel. When you turn, it takes effort to move away from straight, and you feel continued pressure to return to straight. If you let go of the wheel, it will return to a straight position. This is positive stability. If your car had neutral stability, it would take much less effort (ie no resistance) to move away from the straight position, and if you let go of the wheel, it would stay in the turned position you left it in. If you had negative stability, turning the wheel would induce a force in the direction of your turn, encouraging and pulling the wheel further into the direction of turn. Letting go of the wheel would cause a turn to full lock. As you can imagine, this negative stability provides much more maneuverability, but requires computes to be able to bring the wheel back to central when the pilot indicates as such through the control column.