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
Stopping an Application from Launching itself at the Startup With Mac OS X
Many a times, you see applications launching themselves at the start up. They not only slow down the start up process but can be very irritating as well. So if you want to stop them from launching every time you boot your MAC, you can try the mentioned steps.
1. Launch System Preferences on your Mac.
2. Select ‘Accounts’ in the lower left part.
3. Now click on ‘Login Items’. This will bring all the applications in a list form. These applications run when at the start up.
4. Select the applications you want to remove and select the checkbox to hide it. This will take care of it.
Now reboot and see the results yourself. The applications you selected would not launch anymore.