Comment 5 for bug 1090741

Sorry for the late answer. Seems like launchpad changed bug notification :-(

The problem is because blkid seems to hang on some systems.

blkid is used by grub customizer for:

    generating new menuentries after choosing the partition
    displaying partition inside of menuentry details
    environment switch (important when running from live cd, not when using installed systems)

Here's a workaround:

sudo bash -c 'mv /sbin/blkid /sbin/blkid.bak; grub-customizer; mv /sbin/blkid.bak /sbin/blkid'

This disables blkid while running Grub Customizer.

https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/1044111