I had a similar issue before, though I don't remember an error message....
Are you trying to enter the password right away? With the issue I had, if I entered the password too soon, it wouldn't register it and wouldn't boot. If I waited 5 minutes or so before entering it, it would work (must have been still reading data in the background or something and was too soon for the decryption process to start).
You might try restarting it and just waiting 5 minutes or more to enter the password.