Okay....I wouldn't imagine then it was permalinks.
If you don't knwo what the wp-config file is then that may be your problem.
The error appears to be from the database connection. Inside the wp-config files is the database user, database password, database name, etc. which is used to connect to the database.
If you didnt set that up, someone had to because you say it was once working (or am I assuming it worked).
I dont know what hosting service you are using but if you have access to the FTP, the wp-config file should be in the htdocs or httpdocs folder.