This is very normal in 'nix' systems. '' indicates a locked account. (I've given up figuring out how to escape an asterisk)

ex:

  daemon:*:1:1::0:0:Owner of many system processes:/root:/usr/sbin/nologin
  operator:*:2:5::0:0:System &:/:/usr/sbin/nologin
  bin:*:3:7::0:0:Binaries Commands and Source:/:/usr/sbin/nologin
  tty:*:4:65533::0:0:Tty Sandbox:/:/usr/sbin/nologin

If the OS is letting you in with a '*'in the encrypted password field, something is very very wrong.