I am assuming that you have been able to access the reporting server before with the same username and password. But from the log, the username or password is incorrect. I would check that SQL, MOM and FCS are using the same database and are accessing with the same username and password
I created two or three user accounts for using FCS. Each one is for SQL, MOM, and MOM DTS. In the installation (and the document) refers that. If I need to use one account for all services, please me notify me.
However, the first days it works with out problems. Only the report area (14-day) is not working yet (since the installation).