I managed to work around it myself. Here are the steps

  1. Boot to Live CD
  2. Mount ubuntu partition and disable cups-browsed startup script

    sudo mount /dev/mapper/nvidia_abcdefg1 /mnt
    sudo chroot /mnt
    mv /etc/init/cups-browsed.conf /etc/init/cups-browsed.conf.disabled
    nano /etc/init/cups-browsed.conf.disabled   # comment out the code for `start on` then save the changes
    exit
    sudo umount /mnt
    exit
    
  3. restart and boot as usual

This is not removing source of the problem, but at least I can now boot into OS.