Message mixer, odd error returned?

Does anyone know why I am getting this error. I am on step 6, trying to call 'node message-mixer.js caesar 4 ’

$ node mesage-mixer.js caesar 4
shell-init: error retrieving current directory: getcwd: cannot access parent directories: No such file or directory
path.js:1142
cwd = process.cwd();
^

Error: ENOENT: no such file or directory, uv_cwd
at Object.resolve (path.js:1142:25)
at startup (bootstrap_node.js:129:32)
at bootstrap_node.js:542:3
$

I closed it down and started again. Working now