Error Establishing Database Connection

I’ve been receiving this error message while working in my WP Dashboard.

Error establishing a database connection

This either means that the username and password information in your wp-config.php file is incorrect or we can’t contact the database server at mysql. This could mean your host’s database server is down.

Are you sure you have the correct username and password?
Are you sure that you have typed the correct hostname?
Are you sure that the database server is running?

If you’re unsure what these terms mean you should probably contact your host. If you still need help you can always visit the WordPress Support Forums.

This began on Friday, and at first I could clear the message just by refreshing, but by Saturday I couldn’t access the blog or the dashboard at all. I fired up a new blog and deleted the old one, and it worked fine for a while, but now I’m receiving the message again.

Is this a problem with WordPress, my host (Yahoo! Small Business, if it helps), or something else? Do you have any advice for me?

Thank you.