Default LinuxMCE Admin site password
See also How do I login to a Linux console?.
What is the default password for LinuxMCE Web Admin page?
It' s the user(s) you have created when you run the setup Wizard (house setup), the password is the same with the user name, unless you changed it on purpose.
If you haven't got to run the setup wizard and accessed the web admin, first time you are prompted a message saying there are no users in the database and you need to create one, and there you give a username and a password.