Run Toribash as an administrator. You might need to set proper permissions that will allow the login file to be written to your Toribash directory.
If that doesn't work, you can try creating the login file by yourself. Create a file in Notepad named "tb_login.dat" without the quotes. Paste this and change the underlined values to your username and password.
user username
pass password
Save the file to your Toribash directory and open the game.