Same issue when upgrading from Ubuntu 14.04 to 16.04. Note - using LUKS encryption and have nVidia video.
Did a fresh install of Ubuntu 16.04 using LUKS encryption which installed 4.4.0-21 and login worked until I ran upgrades (which installed 4.4.0-34). Now have the cannot type characters into the box to unlock the disk problem again.
Notes:
* If I boot in recovery mode I can enter password, just not with a normal boot.
* If a change my /etc/grub/default to be "quite nosplash", I can enter password in text mode.
Same issue when upgrading from Ubuntu 14.04 to 16.04. Note - using LUKS encryption and have nVidia video.
Did a fresh install of Ubuntu 16.04 using LUKS encryption which installed 4.4.0-21 and login worked until I ran upgrades (which installed 4.4.0-34). Now have the cannot type characters into the box to unlock the disk problem again.
Notes:
* If I boot in recovery mode I can enter password, just not with a normal boot.
* If a change my /etc/grub/default to be "quite nosplash", I can enter password in text mode.
System info:
* System76 Leopard Extreme
* 1 GB nVidia GeForce GTX 750