It's not really a bug, because your php version is too old.
Like described here https://github.com/cartalyst/sentry/issues/98 Sentry checks the computed hashed password. Because of your old php version (<=5.3.7) Sentry uses bcrypt instead of DES. Sentry doesn't support bcrpyt anymore so you got an exception. Of course the exception is a bit confusing, but you can simply fix this issue. Just upgrade your php version at least to 5.4 and it should work.