Joomla - Can't login to to admin area.

We ran into a problem with one of our Joomla installs... We suddenly started receiving this error when we'd attempt to login to the admin area from the frontend, or backend. "Forbidden You don't have permission to access /administrator/[login to view URL] on this server. Additionally, a 404 Not Found error was encountered while trying to use an Error Document to handle the request. " The website still displays fine.. so, it's not an issue with the connection to a database. We're looking for trustworthy someone that's skilled in all things Joomla 1.0x to take a look at our problem and provide a solution. Thanks so much.