I have upgraded my System with full disk encryption from 14.10 to 15.04, and now i'm not able anymore to input my passphrase at boot and therefore can't access my system anymore.
Strangely it worked the first few times but today it suddenly stopped working. Also the keyboard is recognized in the BIOS and works in the GRUB menu.
Finally by taking out the hard disk from my computer and installing it in my laptop i am able to input the passphrase with the keyboard of my laptop.
I remember having this problem about one or two years ago, at this time the problem solved itself by a system update i installed by using my laptop.
Does anybody know a solution to this problem other than hoping a system update will fix it?