Comment 4 for bug 718044

How to boot an encrypted disk with the plymouth "Black Screen of Death" bug:

OK, let's assume you have only one kernel and only one initramfs. If you have older kernels installed, their initramfs images contain the older versions of plymouth unless you ran update-initramfs -u -k all by hand at some point. Doing this on a non-encrypted machine or after unlocking from Busybox, of course, would be a definitive test to see if this is kernel related at all.

With splash removed from the command line, your console works but cryptsetup's "cryptroot" script obviously does not. Neither does the custom script I use to unlock many disks from one password, for that matter. Init's root volume search will time out, and a Busybox shell will spawn. Now you can run cryptsetup manually, and it works fine, exactly like unlocking but not mounting an encrypted flash drive from the command line.

 If you arre not using LVM on your encrypted volume, you must remember the exact name of the root device from /proc/cmdline or use cat /proc/cmdline to bring it up. If you are using LVM, any name for the /dev/mapper device will work, though you still need the correct source device. Your root device now exists, so your next command is "exit" causing Busybox to terminate and the boot process to resume. Now you can roll Plymouth back or your kernel back even if you only had one kernel installed(a bad idea on any alpha).