I guess you are trying to connect with SQL Server authentication, right?
How do you input the password into the Execute Process Task?
Isn't it easier to use the Execute Package Task? (that's why it is there, after all :-))
The editor there has a special input box for the password.
Also make sure that the protection level of the parent package is set correctly, so that the password (which is sensitive data) is remained during execution or after the package has been closed.