$ fsck /dev/sda
Reboot the machine. Same message again. Suddenly noticed that the system date was showing year 2011. Realized that I took out the motherboard's battery but forgot to reconfigure back the system date and time.
Restart again into BIOS settings. Update the system date and time and everything works again.
Next step, update your clock accurately.
$ sudo apt-get install ntpdate $ sudo nptdate ntp.pool.org $ date