My Ubuntu VirtualBox VM upgraded itself two days ago to 14.10.
Now whenever I reboot the text on the enter the passphrase screen is clipped on the edges and I cannot type at all in the textbox (using the mouse, or tab, or enter, or any key).
However, if I manually reboot the machine a second time from VirtualBox the screen displays 'Fast TSC calibration failed' briefly and then the passphrase screen displays correctly and I can type. Always twice to get it to work.
What should do I do to fix this? It was working fine before the upgrade.
(I've tried running all the commands in this answer already: (Statement) "Ubuntu 14.10 won't work because black screen" solution described here)
If I reset the VM at the clipped screen, when Ubuntu boots back up, I get GRUB. I let it load Ubuntu, then I see a text-based interface, where I can then enter the boot password.
This isn't an ideal solution, but at least I can boot.
I reported this bug at https://bugs.launchpad.net/ubuntu/+source/cryptsetup/+bug/1396227.