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
Mojang Set To Release Minecraft 1.3 In August –
Mojang is set to release the next version of Minecraft which is 1.3 on the 1st of next month (August). The new update will include multiple new features such as a new ore which will act as a currency between you and the villagers. Another feature is you can now write in books , This will allow you to communicate with other members.There is also a new texture for gravel.