can't select database error

My site has been up and running for a few months. I recently was doing some tinkering in my index.php file, but everything seemed to work when I left my site last night.

This morning, I try to access my site, and I get this message:

Can’t select database

We were able to connect to the database server (which means your username and password is okay) but not able to select the lavendersbluedesigns_com database.

Are you sure it exists?
Does the user lavendersbluedes have permission to use the lavendersbluedesigns_com database?
On some systems the name of your database is prefixed with your username, so it would be like username_lavendersbluedesigns_com. Could that be the problem?
If you don’t know how to set up a database you should contact your host. If all else fails you may find help at the WordPress Support Forums.

I didn’t change anything in my database or usernames, etc….not sure why I’m getting this message? Please help!

Thanks.