That's my fault not explaining this issue in detail before. To make the password manager work, you have to follow the these instructions:
1) Edit - Preference - General - Remember Password
2) Go to some web which ask for the password and save the password
This process will guaratee the KM's password saving function work and generate the right password file.
3) Tools-Password Manager-Input...
Input the installation pass (not the exe file) for the KM's installation.
4) You should be able to use it now. (You may need to restart, not sure).