I just tried it on ubermix 1.82 and works very well.
Let's try a solution.
First, customize your base image and update your key. Try restoring ubermix using the ESC menu at boot. If all changes are saved, and everything seems to be ok, then do this steps:
1. press ESC at boot, select Normal Boot, press e, and then replace aufs with generic, then CTRL-X.
2. sudo nano /boot/grub/grub.cfg
Locate this section, and add the red text:
menuentry 'Normal Boot' --class ubuntu --class gnu-linux --class gnu --class os {
set gfxpayload=$linux_gfx_mode
insmod part_msdos
insmod ext2
set root='(hd0,msdos1)'
linux /boot/vmlinuz-3.8.5-41-generic root=LABEL=SYSTEM ro quiet splash --no-l$--no-log vt.handoff=7 aufs=restore_both
initrd /boot/initrd.img-3.9.5-41-aufs
}
Save changes, and reboot.
Greetings from the south,
Juan