Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
Samsung Infringed On Apple's Software Based Patents
We have just heard the first from the verdict at the Samsung Vs. Apple Court case which is still on going. The patents infridged by Samsung were Bounce back scrolling , pinch to zoom and tap to zoom.
Bounce Back Scrolling – All devices infringed
Pinch To Zoom – All devices infringed apart from the Ace, Intercept, and Replenish.
Tap To Zoom – All devices infringed apart from the Captivate, Continuum, Gem, Indulge, Nexus S 4G, Transform, and Vibrant.