I too had some trouble logging in to LinuxMCE web admin panel.
I DID read the Install prompts but my username and password didnt work.
and a bunch or others. I recommend doing the password reset as follows if you cant log in, must be a bug. Before you can run these commands you will need to goto your user accounts and enable root then change the password to something you know.
select * FROM Users;
You will see a list of the users in the database. Then type in this:
update Users set Password=md5("mypassword") where UserName="myusername";
Where mypassword is the new password and myusername is the username.